Histograms and polygons
- 2. “Statistics is the science that deals with the method of collecting, classifying, presenting, comparing ,and interpreting numerical data collected to throw some light on any sphere of enquiry.” -Seligman
- 3. Collection of data Organisatio n of data Presentation of data Analysis of data Interpretatio n of data Stage 1 Stage 2 Stage 3 Stage 4 Stage 5
- 4. Each stage of statistical study involves the use of certain techniques or methods Stages Statistical study Statistical tools Stage 1 Collection of data Census or sample method Stage 2 Organisation of data Tally bars Stage 3 Presentation of data Tables, graphs and polygons, histograms etc Stage 4 Analysis of data Percentages ,Averages Stage 5 Interpretation of data Magnitude of percentages
- 5. Graphic representation gives a visual effect. Its used in research work for visual presentation and analysis of data. The graphic method enables us to present data in a simple, clear and effective manner There are many varieties of graphs .Broadly graphs can be divided into two parts: a) Graphs of frequency distribution b) Graphs of time series
- 6. Histogram is joining rectangular diagram of a continuous series in which each rectangle represents the class interval with the frequency .It is a two-dimensional diagram and also called frequency histogram. Cases of constructing a hisogram i. Histogram of equal class interval ii. Histogram when mid points are give iii. Histogram when unequal class intervals
- 8. Scores(mid points) Frequency 5 15 25 35 45 2 5 7 10 4 Ascertainment of lower and upper limits : Get the difference between the first and the second mid point . Divide it by 2 to get the intervals and then draw the histogram.
- 9. Before presenting the data in the form of graphs and frequencies , unequal class intervals are adjusted. Adjustment factor=class interval of concerned class divided by lowest class interval Marks No of students Adjustment factor Frequency density 30-50 50-60 60-70 70-90 90-100 48 30 20 28 16 20/10=2 10/10=1 10/10=1 20/10=2 10/10=1 48/2=24 30/1=30 20/1=20 28/2=14 16/1=16
- 10. Polygon is another form of diagrammatic presentation of data . It is formed by joining all the mid points of the tops of all rectangles .however they can be formed even without constructing a histogram. Frequency polygons can be drawn in two ways: i. With a histogram ii. Without a histogram
- 11. Class limits No of sareees 100-200 200-300 300-400 400-500 500-600 600-700 700-800 10 27 37 24 20 15 10 The total area excluded from the histogram is equal to the area included under frequency polygon
- 13. THANK YOU