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Sampling techniques

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Mukut Deori

This document discusses various sampling techniques used in research. It defines key terms like population, sample, sampling element, and sampling frame. It also explains different types of sampling methods - probability sampling which includes simple random sampling, stratified random sampling, cluster sampling, multi-stage sampling and multi-phase sampling. Non-probability sampling discussed includes purposive sampling, accidental sampling, quota sampling, systematic sampling, and snowball sampling. The document provides examples and outlines the advantages and disadvantages of each sampling technique.

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SAMPLING TECHNIQUESSAMPLING TECHNIQUES Mukut HazarikaMukut Hazarika ProfessorProfessor Department of EducationDepartment of Education Dibrugarh UniversityDibrugarh University
Population and SamplePopulation and Sample • PopulationPopulation: A population refers to any: A population refers to any collection of specified group of humancollection of specified group of human beings or of non-human entities such asbeings or of non-human entities such as objects, educational institutions, timeobjects, educational institutions, time units, geographical areas, prices of wheatunits, geographical areas, prices of wheat or salaries drawn by individuals.or salaries drawn by individuals. • SampleSample: The representative proportion of: The representative proportion of the population is called a sample.the population is called a sample.
SOME OTHER RELATEDSOME OTHER RELATED TERMSTERMS • Sampling ElementSampling Element : Each entity (person, family,: Each entity (person, family, group, organization) from the population aboutgroup, organization) from the population about which information is collected is called awhich information is collected is called a sampling element.sampling element. • Sampling UnitSampling Unit : This is either a single member: This is either a single member (element) or a collection of members (elements)(element) or a collection of members (elements) subject to data analysis (and selection) in thesubject to data analysis (and selection) in the sample.sample. • Sampling FrameSampling Frame : It refers to the complete list of: It refers to the complete list of all units / elements from which the sample isall units / elements from which the sample is drawn.drawn.
Steps Involved in the process ofSteps Involved in the process of Sampling:Sampling: • Defining the populationDefining the population • Listing the populationListing the population • Selecting a representative sampleSelecting a representative sample • Obtaining an adequate sampleObtaining an adequate sample
Purposes of SamplingPurposes of Sampling • Population in many cases may be so large andPopulation in many cases may be so large and scattered that a complete coverage may be notscattered that a complete coverage may be not possible.possible. • In a short period of time valid and comparableIn a short period of time valid and comparable results can be obtained.results can be obtained. • Sampling is economical since it contains fewerSampling is economical since it contains fewer units.units. • Research projects sometimes may require theResearch projects sometimes may require the destruction of the units being tested. So it savesdestruction of the units being tested. So it saves destruction of units.destruction of units.
Principles of SamplingPrinciples of Sampling The main principle of sampling is that the researcherThe main principle of sampling is that the researcher seeks knowledge about the population by observing aseeks knowledge about the population by observing a fewer units and extend the inference about the sample tofewer units and extend the inference about the sample to the entire population.the entire population. The principles of sampling are :The principles of sampling are : • Sample units must be chosen in a systematic andSample units must be chosen in a systematic and objective manner.objective manner. • Sample units must be clearly defined and easilySample units must be clearly defined and easily identifiable.identifiable. • Sample units must be independent of each other.Sample units must be independent of each other.
Types of SamplingTypes of Sampling • Probability SamplingProbability Sampling • Non-Probability SamplingNon-Probability Sampling
Probability SamplingProbability Sampling Probability Sampling is one in which everyProbability Sampling is one in which every unit of a population has a fixed probability ofunit of a population has a fixed probability of being included in the samplebeing included in the sample.. Conditions to be satisfied for Probability sampling :Conditions to be satisfied for Probability sampling : • Complete list of units to be studied is available.Complete list of units to be studied is available. • Size of the population must be known.Size of the population must be known. • Each element must have an equal chance ofEach element must have an equal chance of being selected.being selected. • The form of the distribution of the trait in theThe form of the distribution of the trait in the population can be reasonably be assumed to bepopulation can be reasonably be assumed to be normal.normal.
• Same units of sample should be used throughoutSame units of sample should be used throughout the study.the study. • The selection process should be based on someThe selection process should be based on some sound criteria and should avoid errors, bias andsound criteria and should avoid errors, bias and distortions.distortions.
Types of Probability SamplingTypes of Probability Sampling • Simple or Unrestricted Random samplingSimple or Unrestricted Random sampling • Stratified Random SamplingStratified Random Sampling • Area or Cluster SamplingArea or Cluster Sampling • Multi-stage SamplingMulti-stage Sampling • Multi-phase SamplingMulti-phase Sampling
Simple or Unrestricted Random SamplingSimple or Unrestricted Random Sampling This technique is applied in a homogeneousThis technique is applied in a homogeneous population. Each unit of the population has anpopulation. Each unit of the population has an equal chance of being selected for the sample.equal chance of being selected for the sample. Methods Adopted :Methods Adopted : • LotteryLottery :: – Step 1 : Constructing the Sampling FrameStep 1 : Constructing the Sampling Frame – Step 2 : Writing numbers listed in the samplingStep 2 : Writing numbers listed in the sampling frame onframe on small pieces of papers and placing them insmall pieces of papers and placing them in somesome vessel.vessel. – Step 3 : Mixing all papers well and drawing out oneStep 3 : Mixing all papers well and drawing out one piecepiece of paper at a time from the vessel.of paper at a time from the vessel. • Using Random Number tableUsing Random Number table..
Stratified Random SamplingStratified Random Sampling This technique is applied in aThis technique is applied in a heterogeneous population.heterogeneous population. • Step I : The population is divided into a numberStep I : The population is divided into a number of homogeneous strata or sub-groupsof homogeneous strata or sub-groups based on one or more criteria.based on one or more criteria. • Step II : A sample is drawn from each stratumStep II : A sample is drawn from each stratum using simple random technique.using simple random technique. Types of Stratified Random Sampling :Types of Stratified Random Sampling : – Proportionate Stratified Random SamplingProportionate Stratified Random Sampling – Dis-proportionate Sratified Random SamplingDis-proportionate Sratified Random Sampling
Proportionate Stratified SamplingProportionate Stratified Sampling Class X Students (1000) Urban (400) Rural (600) Boys (250) Girls (150) Boys (400) Girls (200) 25( 10%) 15(10%) 40(10%) 20(10%)
Disproportionate Stratified SamplingDisproportionate Stratified Sampling Class X Students (1000) Urban (400) Rural (600) Boys (250) Girls (150) Boys (400) Girls (200) 50( 20%) 50(33.3%) 50(12.5%) 50(25%)
Area or ClusterArea or Cluster • Step-I : The population is divided into a numberStep-I : The population is divided into a number of clusters each having a number of units.of clusters each having a number of units. • Step-II : Instead of drawing a single unit clustersStep-II : Instead of drawing a single unit clusters of units are drawn using simple randomof units are drawn using simple random technique.technique. • Step-III : Usually clusters are drawn in multi-Step-III : Usually clusters are drawn in multi- stages.stages. • Step-IV : Usually all the units of the clustersStep-IV : Usually all the units of the clusters drawn are used as the sample.drawn are used as the sample.
Multi-stage Random SamplingMulti-stage Random Sampling In this method, sampling is done in variousIn this method, sampling is done in various stages, but only the sample of the last units isstages, but only the sample of the last units is studiedstudied • Step-I : The population is divided into a number of areasStep-I : The population is divided into a number of areas or clusters.or clusters. • Step-II : A sample of clusters is drawn (1Step-II : A sample of clusters is drawn (1stst Stage)Stage) • Step-III : Each selected cluster is divided into more sub-Step-III : Each selected cluster is divided into more sub- groups ( clusters).groups ( clusters). • Step-IV : A sample of sub-groups is drawn randomlyStep-IV : A sample of sub-groups is drawn randomly (2(2ndnd stage).stage). • Step-V : Sample of units are drawn randomly from theStep-V : Sample of units are drawn randomly from the selected sub-groups (3selected sub-groups (3rdrd stage)stage)
Multi-phase Random SamplingMulti-phase Random Sampling The process in this type of sampling isThe process in this type of sampling is same as in Multi-stage sampling; however,same as in Multi-stage sampling; however, in a Multi-phase sampling, each sample isin a Multi-phase sampling, each sample is adequately studied before another sampleadequately studied before another sample is drawn from it.is drawn from it.
Types of Non-probability SamplingTypes of Non-probability Sampling • Purposive Sampling or JudgmentalPurposive Sampling or Judgmental SamplingSampling • Accidental/Incidental SamplingAccidental/Incidental Sampling • Volunteer SamplingVolunteer Sampling • Quota SamplingQuota Sampling • Systematic SamplingSystematic Sampling • Snow Ball SamplingSnow Ball Sampling
Non-Probability SamplingNon-Probability Sampling Units do not have a fixed probability of beingUnits do not have a fixed probability of being included in the sample. This is usuallyincluded in the sample. This is usually used when sampling frame is notused when sampling frame is not available.available.
Purposive or Judgmental SamplingPurposive or Judgmental Sampling The researcher purposively selects those individuals who areThe researcher purposively selects those individuals who are representative of the population. It is also known as judgmentalrepresentative of the population. It is also known as judgmental sample because the investigator selects the sample on the basis ofsample because the investigator selects the sample on the basis of his/her own judgment.his/her own judgment. Advantages:Advantages: (i) It is less costly and more readily accessible to the(i) It is less costly and more readily accessible to the researcher.researcher. (ii) Purposive sampling guarantees that those individuals will be(ii) Purposive sampling guarantees that those individuals will be included in the sample that are representative of the population.included in the sample that are representative of the population. Disadvantages:Disadvantages: (i) Purposive sampling introduces subjectivity in the sampling(i) Purposive sampling introduces subjectivity in the sampling because too much emphasis is given on the ability of the investigatorbecause too much emphasis is given on the ability of the investigator to assess which element is typical of the population.to assess which element is typical of the population. (ii) In the case of purposive sampling the inferential statistics(ii) In the case of purposive sampling the inferential statistics can’t be used legitimately, because, under all inferential statisticalcan’t be used legitimately, because, under all inferential statistical techniques, there is an assumption of randomness.techniques, there is an assumption of randomness.
Accidental / Incidental SamplingAccidental / Incidental Sampling It refers to a sampling procedure inIt refers to a sampling procedure in which the investigator selects the personswhich the investigator selects the persons who are most conveniently available orwho are most conveniently available or who accidentally come in contact during awho accidentally come in contact during a certain period of time in the research.certain period of time in the research.
Quota SamplingQuota Sampling Steps followedSteps followed :: (i) The population is divided into different(i) The population is divided into different strata.strata. (ii) From each stratum a quota is selected.(ii) From each stratum a quota is selected. Advantages:Advantages: (i) Quota samples are the most satisfactory(i) Quota samples are the most satisfactory means when quick and crude results aremeans when quick and crude results are desired.desired. (ii) It can guarantee the inclusion of(ii) It can guarantee the inclusion of individuals from different strata of population.individuals from different strata of population. (iii) It is less costly.(iii) It is less costly.
Disadvantages:Disadvantages: (i) The selected sample is not(i) The selected sample is not representative of the population becauserepresentative of the population because there is no means of establishingthere is no means of establishing randomness.randomness. (ii) In quota sampling, the investigator(ii) In quota sampling, the investigator selects the most accessible units/ individualsselects the most accessible units/ individuals which may not be typical of the population.which may not be typical of the population.
Systematic SamplingSystematic Sampling This sampling is done by selecting orThis sampling is done by selecting or drawing every nth person from a predetermineddrawing every nth person from a predetermined list of elements or individuals.list of elements or individuals. Advantages:Advantages: (i) Systematic sampling is relatively a quick(i) Systematic sampling is relatively a quick method of obtaining a sample of elements.method of obtaining a sample of elements. (ii) Systematic sampling makes it very easy(ii) Systematic sampling makes it very easy to check whether every nth person has beento check whether every nth person has been selected.selected.
Disadvantages:Disadvantages: (i) Systematic sampling ignores all(i) Systematic sampling ignores all persons between every nth elementpersons between every nth element chosen.chosen. (ii) In systematic sampling, the(ii) In systematic sampling, the sampling error increases if the list issampling error increases if the list is arranged in a particular order, say, the listarranged in a particular order, say, the list increases or decreases with respect toincreases or decreases with respect to some trait such as age, education,some trait such as age, education, income, caste, etc.income, caste, etc.
Snowball SamplingSnowball Sampling Some selected behaviour is usually used as theSome selected behaviour is usually used as the basis of contact and/or association in this type ofbasis of contact and/or association in this type of sampling. Snowball sampling is used for obtaining ansampling. Snowball sampling is used for obtaining an impression of informal social relations among individuals.impression of informal social relations among individuals. Steps followed:Steps followed: (i) At first few respondents are selected who(i) At first few respondents are selected who are known and available to the researcher.are known and available to the researcher. (ii) These respondents give other names who(ii) These respondents give other names who meet the criteria of research.meet the criteria of research. (iii) This process is continued until adequate(iii) This process is continued until adequate number of persons are interviewed or a constellation ofnumber of persons are interviewed or a constellation of friendships converges into some type of a definite socialfriendships converges into some type of a definite social pattern.pattern.
Advantages:Advantages: (i)(i) Snowball sampling is important andSnowball sampling is important and helpful in studying small social grouphelpful in studying small social group and its impact upon formaland its impact upon formal organizational structure.organizational structure. (ii)(ii) This method is employed when theThis method is employed when the target population is unknown or when ittarget population is unknown or when it is difficult to approach the respondentsis difficult to approach the respondents in any other way.in any other way.
Disadvantages:Disadvantages: (i)(i) Snowball sampling becomesSnowball sampling becomes cumbersome and difficult when N iscumbersome and difficult when N is large.large. (ii)(ii) The elements included in sample areThe elements included in sample are dependent on the subjective choices ofdependent on the subjective choices of the originally selected respondents andthe originally selected respondents and thereby introduces some bias in thethereby introduces some bias in the sampling.sampling.
Volunteer SamplingVolunteer Sampling It refers to those sampling in which theIt refers to those sampling in which the respondent himself/herself volunteers torespondent himself/herself volunteers to give information.give information.
SOME RESEARCH PROBLEMS:SOME RESEARCH PROBLEMS: • Mathematical creativity and some socio-Mathematical creativity and some socio- psychological factors of Hindus and Muslims.psychological factors of Hindus and Muslims. • Construction and Standardization of a Multiple-Construction and Standardization of a Multiple- choice Reading Comprehension test.choice Reading Comprehension test. • Achievement Level of Primary School StudentsAchievement Level of Primary School Students at the end of Class IV.at the end of Class IV. • Effects of intervention training on some cognitiveEffects of intervention training on some cognitive abilities.abilities. • A study to determine the effects of exposure toA study to determine the effects of exposure to pre-school education on cognitive abilities.pre-school education on cognitive abilities.
Data-Gathering ToolsData-Gathering Tools The major data-gathering tools of researchThe major data-gathering tools of research are:are: • Psychological TestsPsychological Tests • Inquiry FormsInquiry Forms • ObservationObservation • InterviewInterview • Sociometric TechniqueSociometric Technique
Psychological TestsPsychological Tests Psychological tests are devised to evaluate orPsychological tests are devised to evaluate or measure behaviour in a standardized way for themeasure behaviour in a standardized way for the purpose of selection, classification, predictionpurpose of selection, classification, prediction and guidance as well as for the evaluation ofand guidance as well as for the evaluation of educational programmes. They are designed toeducational programmes. They are designed to measure general mental ability or intelligence,measure general mental ability or intelligence, special abilities or aptitudes, creativity,special abilities or aptitudes, creativity, achievement, personality traits and adjustment,achievement, personality traits and adjustment, interests and values.interests and values.
What are tests ?What are tests ? • Tests consist of a series of tasks whichTests consist of a series of tasks which the subject is required to perform.the subject is required to perform. • Cronbach (1964) defines a test as aCronbach (1964) defines a test as a systematic procedure for comparing thesystematic procedure for comparing the behaviour of two or more persons at abehaviour of two or more persons at a particular time ; or one or more persons atparticular time ; or one or more persons at different time.different time.
Standardized Test:Standardized Test: A standardized test is one that has specificA standardized test is one that has specific directions for administration and scoring, adirections for administration and scoring, a fixed set of test items, and has beenfixed set of test items, and has been administered to representative samplesadministered to representative samples taken from the population for whom thetaken from the population for whom the test is intended for the purpose oftest is intended for the purpose of establishing norms (Koul, 1997).establishing norms (Koul, 1997).
Classification of TestsClassification of Tests • On the basis of Time limit in producing theOn the basis of Time limit in producing the response:response: a) Power Testa) Power Test b) Speed Testb) Speed Test • On the basis of Administrative conditions:On the basis of Administrative conditions: a) Group testa) Group test b) Individual testb) Individual test
• On the basis of Purposes:On the basis of Purposes: a) The Tests of General mental abilitya) The Tests of General mental ability or Intelligenceor Intelligence b) The Tests of Special ability orb) The Tests of Special ability or AptitudesAptitudes c) The Tests of Creativityc) The Tests of Creativity d) The Tests of Attainment ord) The Tests of Attainment or AchievementAchievement e) The Personality measurese) The Personality measures
• On the basis of Standardization:On the basis of Standardization: a) Standardized Testsa) Standardized Tests b) Non-Standardized Teacher madeb) Non-Standardized Teacher made teststests • On the basis of Nature of Items:On the basis of Nature of Items: a) Verbal Testa) Verbal Test b) Nonverbal Testb) Nonverbal Test c) Performance testc) Performance test
• On the basis of Scoring:On the basis of Scoring: a) Objective Type Testa) Objective Type Test b) Essay Type Testb) Essay Type Test
• Power Test:Power Test: A power test is one which has a generousA power test is one which has a generous time limit so that most examinees are abletime limit so that most examinees are able to attempt every item.to attempt every item. • Speed Test:Speed Test: A speed test is one which has severe timeA speed test is one which has severe time limit so that no examinees are able tolimit so that no examinees are able to attempt all items. Speed test measuresattempt all items. Speed test measures how rapidly or with what speed thehow rapidly or with what speed the examinees can respond within a givenexaminees can respond within a given time limit.time limit.
Characteristics of TestsCharacteristics of Tests • ValidityValidity • ReliabilityReliability • UsabilityUsability a) Objectivitya) Objectivity b) Economy of Timeb) Economy of Time c) Costc) Cost d) Ease of Administrationd) Ease of Administration e) Ease of Scoringe) Ease of Scoring f) Ease of Interpretationf) Ease of Interpretation
ValidityValidity Meaning: The term ‘Validity’ meansMeaning: The term ‘Validity’ means truthfulness or fidelity.truthfulness or fidelity. Definition:Definition: • Validity refers to the degree to which a testValidity refers to the degree to which a test measures what it claims to measure.measures what it claims to measure. • The validity of a test concerns what theThe validity of a test concerns what the test measures and how well it does sotest measures and how well it does so (Anastasi, 1988)(Anastasi, 1988)
• Validity of a test is defined as the accuracyValidity of a test is defined as the accuracy with which it measures that which iswith which it measures that which is intended to measure or as the degree tointended to measure or as the degree to which it approaches infallibility inwhich it approaches infallibility in measuring what it purports to measuremeasuring what it purports to measure (Lindquist, 1951)(Lindquist, 1951)
Types of Validity:Types of Validity: • Content ValidityContent Validity • Criterion-Related ValidityCriterion-Related Validity a) Concurrent Validitya) Concurrent Validity b) Predictive Validityb) Predictive Validity • Construct ValidityConstruct Validity
Content validity:Content validity: Content validity is the representativenessContent validity is the representativeness or sampling adequacy of the content – theor sampling adequacy of the content – the substance, the matter, the topics – of asubstance, the matter, the topics – of a measuring instrument. It is estimated bymeasuring instrument. It is estimated by evaluating the relevance of the test items,evaluating the relevance of the test items, in relation to instructional objectives andin relation to instructional objectives and actual subject matter studied.actual subject matter studied.
Criterion-Related Validity:Criterion-Related Validity: Criterion related validity is one which isCriterion related validity is one which is obtained by comparing (or correlating) theobtained by comparing (or correlating) the test scores with scores obtained on atest scores with scores obtained on a criterion available at present or to becriterion available at present or to be available in the future.available in the future. a) Concurrent Validitya) Concurrent Validity :: The degree to which a test isThe degree to which a test is correlated with a criterion which iscorrelated with a criterion which is available at the present time.available at the present time.
b) Predictive Validity:b) Predictive Validity: The degree to which a test isThe degree to which a test is correlated with a criterion which will becorrelated with a criterion which will be available in the future. It refers to theavailable in the future. It refers to the association between present results asassociation between present results as indicated by a test and future behaviour.indicated by a test and future behaviour.
Construct ValidityConstruct Validity :: The degree to which certain psychological traitsThe degree to which certain psychological traits or constructs are actually represented by testor constructs are actually represented by test performance. Construct validation is an analysisperformance. Construct validation is an analysis of the meaning of test scores in terms ofof the meaning of test scores in terms of psychological constructs (Cronbach and Meehl ,psychological constructs (Cronbach and Meehl , 1955).1955). Example: If a test is designed to measureExample: If a test is designed to measure emotional stability, what kinds of evidence areemotional stability, what kinds of evidence are necessary before we can have confidence thatnecessary before we can have confidence that the information provided by the test reflects thisthe information provided by the test reflects this factor ?factor ?

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Sampling techniques

  • 1. SAMPLING TECHNIQUESSAMPLING TECHNIQUES Mukut HazarikaMukut Hazarika ProfessorProfessor Department of EducationDepartment of Education Dibrugarh UniversityDibrugarh University
  • 2. Population and SamplePopulation and Sample • PopulationPopulation: A population refers to any: A population refers to any collection of specified group of humancollection of specified group of human beings or of non-human entities such asbeings or of non-human entities such as objects, educational institutions, timeobjects, educational institutions, time units, geographical areas, prices of wheatunits, geographical areas, prices of wheat or salaries drawn by individuals.or salaries drawn by individuals. • SampleSample: The representative proportion of: The representative proportion of the population is called a sample.the population is called a sample.
  • 3. SOME OTHER RELATEDSOME OTHER RELATED TERMSTERMS • Sampling ElementSampling Element : Each entity (person, family,: Each entity (person, family, group, organization) from the population aboutgroup, organization) from the population about which information is collected is called awhich information is collected is called a sampling element.sampling element. • Sampling UnitSampling Unit : This is either a single member: This is either a single member (element) or a collection of members (elements)(element) or a collection of members (elements) subject to data analysis (and selection) in thesubject to data analysis (and selection) in the sample.sample. • Sampling FrameSampling Frame : It refers to the complete list of: It refers to the complete list of all units / elements from which the sample isall units / elements from which the sample is drawn.drawn.
  • 4. Steps Involved in the process ofSteps Involved in the process of Sampling:Sampling: • Defining the populationDefining the population • Listing the populationListing the population • Selecting a representative sampleSelecting a representative sample • Obtaining an adequate sampleObtaining an adequate sample
  • 5. Purposes of SamplingPurposes of Sampling • Population in many cases may be so large andPopulation in many cases may be so large and scattered that a complete coverage may be notscattered that a complete coverage may be not possible.possible. • In a short period of time valid and comparableIn a short period of time valid and comparable results can be obtained.results can be obtained. • Sampling is economical since it contains fewerSampling is economical since it contains fewer units.units. • Research projects sometimes may require theResearch projects sometimes may require the destruction of the units being tested. So it savesdestruction of the units being tested. So it saves destruction of units.destruction of units.
  • 6. Principles of SamplingPrinciples of Sampling The main principle of sampling is that the researcherThe main principle of sampling is that the researcher seeks knowledge about the population by observing aseeks knowledge about the population by observing a fewer units and extend the inference about the sample tofewer units and extend the inference about the sample to the entire population.the entire population. The principles of sampling are :The principles of sampling are : • Sample units must be chosen in a systematic andSample units must be chosen in a systematic and objective manner.objective manner. • Sample units must be clearly defined and easilySample units must be clearly defined and easily identifiable.identifiable. • Sample units must be independent of each other.Sample units must be independent of each other.
  • 7. Types of SamplingTypes of Sampling • Probability SamplingProbability Sampling • Non-Probability SamplingNon-Probability Sampling
  • 8. Probability SamplingProbability Sampling Probability Sampling is one in which everyProbability Sampling is one in which every unit of a population has a fixed probability ofunit of a population has a fixed probability of being included in the samplebeing included in the sample.. Conditions to be satisfied for Probability sampling :Conditions to be satisfied for Probability sampling : • Complete list of units to be studied is available.Complete list of units to be studied is available. • Size of the population must be known.Size of the population must be known. • Each element must have an equal chance ofEach element must have an equal chance of being selected.being selected. • The form of the distribution of the trait in theThe form of the distribution of the trait in the population can be reasonably be assumed to bepopulation can be reasonably be assumed to be normal.normal.
  • 9. • Same units of sample should be used throughoutSame units of sample should be used throughout the study.the study. • The selection process should be based on someThe selection process should be based on some sound criteria and should avoid errors, bias andsound criteria and should avoid errors, bias and distortions.distortions.
  • 10. Types of Probability SamplingTypes of Probability Sampling • Simple or Unrestricted Random samplingSimple or Unrestricted Random sampling • Stratified Random SamplingStratified Random Sampling • Area or Cluster SamplingArea or Cluster Sampling • Multi-stage SamplingMulti-stage Sampling • Multi-phase SamplingMulti-phase Sampling
  • 11. Simple or Unrestricted Random SamplingSimple or Unrestricted Random Sampling This technique is applied in a homogeneousThis technique is applied in a homogeneous population. Each unit of the population has anpopulation. Each unit of the population has an equal chance of being selected for the sample.equal chance of being selected for the sample. Methods Adopted :Methods Adopted : • LotteryLottery :: – Step 1 : Constructing the Sampling FrameStep 1 : Constructing the Sampling Frame – Step 2 : Writing numbers listed in the samplingStep 2 : Writing numbers listed in the sampling frame onframe on small pieces of papers and placing them insmall pieces of papers and placing them in somesome vessel.vessel. – Step 3 : Mixing all papers well and drawing out oneStep 3 : Mixing all papers well and drawing out one piecepiece of paper at a time from the vessel.of paper at a time from the vessel. • Using Random Number tableUsing Random Number table..
  • 12. Stratified Random SamplingStratified Random Sampling This technique is applied in aThis technique is applied in a heterogeneous population.heterogeneous population. • Step I : The population is divided into a numberStep I : The population is divided into a number of homogeneous strata or sub-groupsof homogeneous strata or sub-groups based on one or more criteria.based on one or more criteria. • Step II : A sample is drawn from each stratumStep II : A sample is drawn from each stratum using simple random technique.using simple random technique. Types of Stratified Random Sampling :Types of Stratified Random Sampling : – Proportionate Stratified Random SamplingProportionate Stratified Random Sampling – Dis-proportionate Sratified Random SamplingDis-proportionate Sratified Random Sampling
  • 13. Proportionate Stratified SamplingProportionate Stratified Sampling Class X Students (1000) Urban (400) Rural (600) Boys (250) Girls (150) Boys (400) Girls (200) 25( 10%) 15(10%) 40(10%) 20(10%)
  • 14. Disproportionate Stratified SamplingDisproportionate Stratified Sampling Class X Students (1000) Urban (400) Rural (600) Boys (250) Girls (150) Boys (400) Girls (200) 50( 20%) 50(33.3%) 50(12.5%) 50(25%)
  • 15. Area or ClusterArea or Cluster • Step-I : The population is divided into a numberStep-I : The population is divided into a number of clusters each having a number of units.of clusters each having a number of units. • Step-II : Instead of drawing a single unit clustersStep-II : Instead of drawing a single unit clusters of units are drawn using simple randomof units are drawn using simple random technique.technique. • Step-III : Usually clusters are drawn in multi-Step-III : Usually clusters are drawn in multi- stages.stages. • Step-IV : Usually all the units of the clustersStep-IV : Usually all the units of the clusters drawn are used as the sample.drawn are used as the sample.
  • 16. Multi-stage Random SamplingMulti-stage Random Sampling In this method, sampling is done in variousIn this method, sampling is done in various stages, but only the sample of the last units isstages, but only the sample of the last units is studiedstudied • Step-I : The population is divided into a number of areasStep-I : The population is divided into a number of areas or clusters.or clusters. • Step-II : A sample of clusters is drawn (1Step-II : A sample of clusters is drawn (1stst Stage)Stage) • Step-III : Each selected cluster is divided into more sub-Step-III : Each selected cluster is divided into more sub- groups ( clusters).groups ( clusters). • Step-IV : A sample of sub-groups is drawn randomlyStep-IV : A sample of sub-groups is drawn randomly (2(2ndnd stage).stage). • Step-V : Sample of units are drawn randomly from theStep-V : Sample of units are drawn randomly from the selected sub-groups (3selected sub-groups (3rdrd stage)stage)
  • 17. Multi-phase Random SamplingMulti-phase Random Sampling The process in this type of sampling isThe process in this type of sampling is same as in Multi-stage sampling; however,same as in Multi-stage sampling; however, in a Multi-phase sampling, each sample isin a Multi-phase sampling, each sample is adequately studied before another sampleadequately studied before another sample is drawn from it.is drawn from it.
  • 18. Types of Non-probability SamplingTypes of Non-probability Sampling • Purposive Sampling or JudgmentalPurposive Sampling or Judgmental SamplingSampling • Accidental/Incidental SamplingAccidental/Incidental Sampling • Volunteer SamplingVolunteer Sampling • Quota SamplingQuota Sampling • Systematic SamplingSystematic Sampling • Snow Ball SamplingSnow Ball Sampling
  • 19. Non-Probability SamplingNon-Probability Sampling Units do not have a fixed probability of beingUnits do not have a fixed probability of being included in the sample. This is usuallyincluded in the sample. This is usually used when sampling frame is notused when sampling frame is not available.available.
  • 20. Purposive or Judgmental SamplingPurposive or Judgmental Sampling The researcher purposively selects those individuals who areThe researcher purposively selects those individuals who are representative of the population. It is also known as judgmentalrepresentative of the population. It is also known as judgmental sample because the investigator selects the sample on the basis ofsample because the investigator selects the sample on the basis of his/her own judgment.his/her own judgment. Advantages:Advantages: (i) It is less costly and more readily accessible to the(i) It is less costly and more readily accessible to the researcher.researcher. (ii) Purposive sampling guarantees that those individuals will be(ii) Purposive sampling guarantees that those individuals will be included in the sample that are representative of the population.included in the sample that are representative of the population. Disadvantages:Disadvantages: (i) Purposive sampling introduces subjectivity in the sampling(i) Purposive sampling introduces subjectivity in the sampling because too much emphasis is given on the ability of the investigatorbecause too much emphasis is given on the ability of the investigator to assess which element is typical of the population.to assess which element is typical of the population. (ii) In the case of purposive sampling the inferential statistics(ii) In the case of purposive sampling the inferential statistics can’t be used legitimately, because, under all inferential statisticalcan’t be used legitimately, because, under all inferential statistical techniques, there is an assumption of randomness.techniques, there is an assumption of randomness.
  • 21. Accidental / Incidental SamplingAccidental / Incidental Sampling It refers to a sampling procedure inIt refers to a sampling procedure in which the investigator selects the personswhich the investigator selects the persons who are most conveniently available orwho are most conveniently available or who accidentally come in contact during awho accidentally come in contact during a certain period of time in the research.certain period of time in the research.
  • 22. Quota SamplingQuota Sampling Steps followedSteps followed :: (i) The population is divided into different(i) The population is divided into different strata.strata. (ii) From each stratum a quota is selected.(ii) From each stratum a quota is selected. Advantages:Advantages: (i) Quota samples are the most satisfactory(i) Quota samples are the most satisfactory means when quick and crude results aremeans when quick and crude results are desired.desired. (ii) It can guarantee the inclusion of(ii) It can guarantee the inclusion of individuals from different strata of population.individuals from different strata of population. (iii) It is less costly.(iii) It is less costly.
  • 23. Disadvantages:Disadvantages: (i) The selected sample is not(i) The selected sample is not representative of the population becauserepresentative of the population because there is no means of establishingthere is no means of establishing randomness.randomness. (ii) In quota sampling, the investigator(ii) In quota sampling, the investigator selects the most accessible units/ individualsselects the most accessible units/ individuals which may not be typical of the population.which may not be typical of the population.
  • 24. Systematic SamplingSystematic Sampling This sampling is done by selecting orThis sampling is done by selecting or drawing every nth person from a predetermineddrawing every nth person from a predetermined list of elements or individuals.list of elements or individuals. Advantages:Advantages: (i) Systematic sampling is relatively a quick(i) Systematic sampling is relatively a quick method of obtaining a sample of elements.method of obtaining a sample of elements. (ii) Systematic sampling makes it very easy(ii) Systematic sampling makes it very easy to check whether every nth person has beento check whether every nth person has been selected.selected.
  • 25. Disadvantages:Disadvantages: (i) Systematic sampling ignores all(i) Systematic sampling ignores all persons between every nth elementpersons between every nth element chosen.chosen. (ii) In systematic sampling, the(ii) In systematic sampling, the sampling error increases if the list issampling error increases if the list is arranged in a particular order, say, the listarranged in a particular order, say, the list increases or decreases with respect toincreases or decreases with respect to some trait such as age, education,some trait such as age, education, income, caste, etc.income, caste, etc.
  • 26. Snowball SamplingSnowball Sampling Some selected behaviour is usually used as theSome selected behaviour is usually used as the basis of contact and/or association in this type ofbasis of contact and/or association in this type of sampling. Snowball sampling is used for obtaining ansampling. Snowball sampling is used for obtaining an impression of informal social relations among individuals.impression of informal social relations among individuals. Steps followed:Steps followed: (i) At first few respondents are selected who(i) At first few respondents are selected who are known and available to the researcher.are known and available to the researcher. (ii) These respondents give other names who(ii) These respondents give other names who meet the criteria of research.meet the criteria of research. (iii) This process is continued until adequate(iii) This process is continued until adequate number of persons are interviewed or a constellation ofnumber of persons are interviewed or a constellation of friendships converges into some type of a definite socialfriendships converges into some type of a definite social pattern.pattern.
  • 27. Advantages:Advantages: (i)(i) Snowball sampling is important andSnowball sampling is important and helpful in studying small social grouphelpful in studying small social group and its impact upon formaland its impact upon formal organizational structure.organizational structure. (ii)(ii) This method is employed when theThis method is employed when the target population is unknown or when ittarget population is unknown or when it is difficult to approach the respondentsis difficult to approach the respondents in any other way.in any other way.
  • 28. Disadvantages:Disadvantages: (i)(i) Snowball sampling becomesSnowball sampling becomes cumbersome and difficult when N iscumbersome and difficult when N is large.large. (ii)(ii) The elements included in sample areThe elements included in sample are dependent on the subjective choices ofdependent on the subjective choices of the originally selected respondents andthe originally selected respondents and thereby introduces some bias in thethereby introduces some bias in the sampling.sampling.
  • 29. Volunteer SamplingVolunteer Sampling It refers to those sampling in which theIt refers to those sampling in which the respondent himself/herself volunteers torespondent himself/herself volunteers to give information.give information.
  • 30. SOME RESEARCH PROBLEMS:SOME RESEARCH PROBLEMS: • Mathematical creativity and some socio-Mathematical creativity and some socio- psychological factors of Hindus and Muslims.psychological factors of Hindus and Muslims. • Construction and Standardization of a Multiple-Construction and Standardization of a Multiple- choice Reading Comprehension test.choice Reading Comprehension test. • Achievement Level of Primary School StudentsAchievement Level of Primary School Students at the end of Class IV.at the end of Class IV. • Effects of intervention training on some cognitiveEffects of intervention training on some cognitive abilities.abilities. • A study to determine the effects of exposure toA study to determine the effects of exposure to pre-school education on cognitive abilities.pre-school education on cognitive abilities.
  • 31. Data-Gathering ToolsData-Gathering Tools The major data-gathering tools of researchThe major data-gathering tools of research are:are: • Psychological TestsPsychological Tests • Inquiry FormsInquiry Forms • ObservationObservation • InterviewInterview • Sociometric TechniqueSociometric Technique
  • 32. Psychological TestsPsychological Tests Psychological tests are devised to evaluate orPsychological tests are devised to evaluate or measure behaviour in a standardized way for themeasure behaviour in a standardized way for the purpose of selection, classification, predictionpurpose of selection, classification, prediction and guidance as well as for the evaluation ofand guidance as well as for the evaluation of educational programmes. They are designed toeducational programmes. They are designed to measure general mental ability or intelligence,measure general mental ability or intelligence, special abilities or aptitudes, creativity,special abilities or aptitudes, creativity, achievement, personality traits and adjustment,achievement, personality traits and adjustment, interests and values.interests and values.
  • 33. What are tests ?What are tests ? • Tests consist of a series of tasks whichTests consist of a series of tasks which the subject is required to perform.the subject is required to perform. • Cronbach (1964) defines a test as aCronbach (1964) defines a test as a systematic procedure for comparing thesystematic procedure for comparing the behaviour of two or more persons at abehaviour of two or more persons at a particular time ; or one or more persons atparticular time ; or one or more persons at different time.different time.
  • 34. Standardized Test:Standardized Test: A standardized test is one that has specificA standardized test is one that has specific directions for administration and scoring, adirections for administration and scoring, a fixed set of test items, and has beenfixed set of test items, and has been administered to representative samplesadministered to representative samples taken from the population for whom thetaken from the population for whom the test is intended for the purpose oftest is intended for the purpose of establishing norms (Koul, 1997).establishing norms (Koul, 1997).
  • 35. Classification of TestsClassification of Tests • On the basis of Time limit in producing theOn the basis of Time limit in producing the response:response: a) Power Testa) Power Test b) Speed Testb) Speed Test • On the basis of Administrative conditions:On the basis of Administrative conditions: a) Group testa) Group test b) Individual testb) Individual test
  • 36. • On the basis of Purposes:On the basis of Purposes: a) The Tests of General mental abilitya) The Tests of General mental ability or Intelligenceor Intelligence b) The Tests of Special ability orb) The Tests of Special ability or AptitudesAptitudes c) The Tests of Creativityc) The Tests of Creativity d) The Tests of Attainment ord) The Tests of Attainment or AchievementAchievement e) The Personality measurese) The Personality measures
  • 37. • On the basis of Standardization:On the basis of Standardization: a) Standardized Testsa) Standardized Tests b) Non-Standardized Teacher madeb) Non-Standardized Teacher made teststests • On the basis of Nature of Items:On the basis of Nature of Items: a) Verbal Testa) Verbal Test b) Nonverbal Testb) Nonverbal Test c) Performance testc) Performance test
  • 38. • On the basis of Scoring:On the basis of Scoring: a) Objective Type Testa) Objective Type Test b) Essay Type Testb) Essay Type Test
  • 39. • Power Test:Power Test: A power test is one which has a generousA power test is one which has a generous time limit so that most examinees are abletime limit so that most examinees are able to attempt every item.to attempt every item. • Speed Test:Speed Test: A speed test is one which has severe timeA speed test is one which has severe time limit so that no examinees are able tolimit so that no examinees are able to attempt all items. Speed test measuresattempt all items. Speed test measures how rapidly or with what speed thehow rapidly or with what speed the examinees can respond within a givenexaminees can respond within a given time limit.time limit.
  • 40. Characteristics of TestsCharacteristics of Tests • ValidityValidity • ReliabilityReliability • UsabilityUsability a) Objectivitya) Objectivity b) Economy of Timeb) Economy of Time c) Costc) Cost d) Ease of Administrationd) Ease of Administration e) Ease of Scoringe) Ease of Scoring f) Ease of Interpretationf) Ease of Interpretation
  • 41. ValidityValidity Meaning: The term ‘Validity’ meansMeaning: The term ‘Validity’ means truthfulness or fidelity.truthfulness or fidelity. Definition:Definition: • Validity refers to the degree to which a testValidity refers to the degree to which a test measures what it claims to measure.measures what it claims to measure. • The validity of a test concerns what theThe validity of a test concerns what the test measures and how well it does sotest measures and how well it does so (Anastasi, 1988)(Anastasi, 1988)
  • 42. • Validity of a test is defined as the accuracyValidity of a test is defined as the accuracy with which it measures that which iswith which it measures that which is intended to measure or as the degree tointended to measure or as the degree to which it approaches infallibility inwhich it approaches infallibility in measuring what it purports to measuremeasuring what it purports to measure (Lindquist, 1951)(Lindquist, 1951)
  • 43. Types of Validity:Types of Validity: • Content ValidityContent Validity • Criterion-Related ValidityCriterion-Related Validity a) Concurrent Validitya) Concurrent Validity b) Predictive Validityb) Predictive Validity • Construct ValidityConstruct Validity
  • 44. Content validity:Content validity: Content validity is the representativenessContent validity is the representativeness or sampling adequacy of the content – theor sampling adequacy of the content – the substance, the matter, the topics – of asubstance, the matter, the topics – of a measuring instrument. It is estimated bymeasuring instrument. It is estimated by evaluating the relevance of the test items,evaluating the relevance of the test items, in relation to instructional objectives andin relation to instructional objectives and actual subject matter studied.actual subject matter studied.
  • 45. Criterion-Related Validity:Criterion-Related Validity: Criterion related validity is one which isCriterion related validity is one which is obtained by comparing (or correlating) theobtained by comparing (or correlating) the test scores with scores obtained on atest scores with scores obtained on a criterion available at present or to becriterion available at present or to be available in the future.available in the future. a) Concurrent Validitya) Concurrent Validity :: The degree to which a test isThe degree to which a test is correlated with a criterion which iscorrelated with a criterion which is available at the present time.available at the present time.
  • 46. b) Predictive Validity:b) Predictive Validity: The degree to which a test isThe degree to which a test is correlated with a criterion which will becorrelated with a criterion which will be available in the future. It refers to theavailable in the future. It refers to the association between present results asassociation between present results as indicated by a test and future behaviour.indicated by a test and future behaviour.
  • 47. Construct ValidityConstruct Validity :: The degree to which certain psychological traitsThe degree to which certain psychological traits or constructs are actually represented by testor constructs are actually represented by test performance. Construct validation is an analysisperformance. Construct validation is an analysis of the meaning of test scores in terms ofof the meaning of test scores in terms of psychological constructs (Cronbach and Meehl ,psychological constructs (Cronbach and Meehl , 1955).1955). Example: If a test is designed to measureExample: If a test is designed to measure emotional stability, what kinds of evidence areemotional stability, what kinds of evidence are necessary before we can have confidence thatnecessary before we can have confidence that the information provided by the test reflects thisthe information provided by the test reflects this factor ?factor ?