Sampling techniquesmod5

Sampling Techniques

Module 5
Santa Rosa Science And Technology High
School
Basic Statistics
Ms. Ma. Cristina C. Pegollo

Sample Problem

Suppose Ms. Bambasi wants to
determine the weekly food
expenditure of students, if there are
1000 students and the guidance
counselor decided to use only 100
students as a sample, who will be
included in the sample?

DEFINITION

Sampling technique is a
procedure used to determine
the individuals or members of a
sample.

Sampling Techniques

Probability Non-Probability
Sampling Sampling

Convenience
Random Sampling Sampling

Systematic Quota Sampling
Sampling

Stratified Random Purposive
Sampling Sampling

Cluster Sampling

Multi-Stage
Sampling

PROBABILITY Sampling
each eligible member of the population
has a specific and known chance of
being included in the sample.
When using this technique, it is important
to have a complete list of the members
of the population

NON-PROBABILITY Sampling

Members of the sample size are drawn
based on the judgment of the
researcher.
Sometimes, referred to as subjective
sampling.

Probability Sampling
1. Simple Random Sampling
 Lottery Method - write the names or codes on a
piece of paper, put them in a
container, then randomly
select the desired number of
samples. Sometimes referred to as the
fishbowl technique.

1. Simple Random Sampling
 Random Numbers – a table of random numbers,
computer or calculator can be used to generate
random numbers. This is perhaps a more
convenient way of selecting your random sample.
The randomly produced digits can be used to pick
your samples. However, a complete listing of the
members of the population is needed.

2. Systematic Sampling – choose a
starting point then select every
kth element of the population
using

Example
Choose a sample of size 5 from N = 45, using
systematic random sampling.
Solution:
Step 1: Determine k; , this means that
you have to include every 9th member of the
population after choosing a random start.
Step 2: You can employ the lottery method to get a
random start. Suppose you picked 4.
Step 3: Getting 5 members you will have: 4, 13,
22, 31, and 40

3. Stratified Random Sampling – the
population is subdivided into at
least two different subpopulations
(or strata) that share the same
characteristics (such as gender),
then draw a sample from each
stratum.

Example
Brgy. Market Area consists of 10,000 families
belonging to different income brackets. A survey
to find out how many are in favor of the RH bill
will be conducted. To ensure that all income
groups are represented, respondents will be
divided into High-Income, Average-Income, and
Low-Income. Below is the distribution of income
groups. Strata Number of Families
High – Income 2 000
Average – Income 5 000
Low-Income 3 000
N = 10 000

Cont…
1. Using a 5% margin of error, how many families
should be included in the sample? Using
Slovin’s Formula, you should get 385.
2. Using either proportional or equal allocation ,
how many from each group should be taken as
samples? See the table below
Strata Number Percent Proportional Equal
of
Families
High-Income 2 000 0.2(385) = 77 385/3 = 128

Average- 5 000 0.5(385) = 129
Income 193
Low- Income 3 000 0.3(385) = 128
115
10 000 100% 385 385

4.Cluster Sampling – divide the
population area into sections (or
clusters), then randomly select a few
of those sections, and then you
randomly select a sample from those
selected sections.

Example
Suppose we want to determine the
average daily expenses of families living
in the City of Santa Rosa. Assume that
there are 15 barangays. We can draw a
random sample of 5 barangays using
random sampling and then get a certain
number of families from each of the 5
barangays.

5. Multi-Stage Sampling – combination of
several sampling techniques
discussed.

Non-Probability Sampling
1. Convenience Sampling – simply use results
that are readily available.
Hey! Do you believe
in love at first sight?

2. Quota Sampling - the researcher first
identifies the stratums and their proportions as
they are represented in the population. Then
convenience or judgment sampling is used to
select the required number of subjects from
each stratum.
Selected
through
researcher’s
convenience or
judgment.

3. Purposive Sampling – selects members or
elements based on the particular purpose of the
experiment or study. This technique is useful for
situations where you need to reach a targeted
sample quickly and where sampling for
proportionality is not the primary concern.

Sample Problem
Suppose Ms. Bambasi wants to
determine the weekly food expenditure
of students, if there are 1000 students
and the guidance counselor decided to
use only 100 students as a sample, who
will be included in the sample?
Activity. With your partner, help Ms.
Bambasi decide on which sampling
technique she should use in selecting
students for her sample. Present her
three choices. (Bond Paper)

Exercises:
Identify which sampling technique was used in the
following scenarios.
1. When she wrote Women and Emoticons, author
KC Pascual based conclusions on 4500
responses from 100,000 questionnaires
distributed to women.
2. The Guidance Counselor at Santa Rosa High
School surveys all students from each of 20
randomly selected classes.
3. A sociologist at the College of StaRSci selects
15 men and 15 women from each of 4 Math
Classes.

Cont…
4. IBM selects every 200th compact disk from the
assembly line ad conducts a thorough test of
quality.
5. The court secretary writes the name of each
Municipal Judge on a separate card, shuffles
the cards , and then draws 3 names.
6. The marketing manager of Ebay.ph tests a new
sales strategy by randomly selecting 150
consumers with less than P100 000 in gross
income and 150 consumers with gross income
of at least P100 000.
7. Pro-RH bill lobbyists polls 300 men and 300
women about their views concerning the use of
contraceptives.

Cont.
8. A market researcher for Champion Detergent
interviews all passengers on each of 10
randomly selected PUVs.
9. A medical researcher from Multiliver Phils.
interviews all leukemia patients in each of 20
randomly selected hospitals.
10. In conducting research for the evening news, a
reported for ABC-CBN interviews 15 people as
they leave SM Santa Rosa.

B. Solve the following
1. A researcher would like to investigate the
perception of students of Mathematics. He
divided the population into sub-populations as
shown below. Use stratified random sampling if
the sample to be drawn consists of 500
students.
Strata Number of
Students
First Year 1600
Second Year 1500
Third Year 1400
Fourth Year 1000

2. A journalist would like to know the most favorite
noontime show for this month. He decided to
conduct a survey on 5 barangays. The table
below shows the list of barangay and the
number of residents in each barangay. Use
stratified random sampling to draw 1 000
residents who will be included in the survey.
Barangay Number of Residents
Mapayapa 2 000
Malinis 1 000
Mahangin 1 500
Mabunga 2 500
Masaya 1 500

Sampling techniquesmod5

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