Representation of data using bar diagram

Representation of data using bar diagram and its interpretation

1. REPRESENTATION OF DATA USING BAR DIAGRAM & INTERPRETATION OF BAR DIAGRAM Subject: ASSESSMENT IN EDUCATION Presented by, Saranya S Nair Physical Science

2. Statistics includes collection and analysis of data. Presentation of the collected information in an attractive and informative form is also an important function of statistics. Tabular presentation is one form of presenting data. But people have more affinity towards pictures or diagrams. INTRODUCTION

3. Data which fall into different categories or qualitative classes is called categorical data. EXAMPLES: Observations on geographical or chronological characteristics like populations of different countries Population of a country in different years Amounts spents or different items of expenditure by a family etc. Contd …

4. One dimensional diagrams like bar diagrams. Two dimensional diagrams like rectangles, squares and circles. Three dimensional diagrams like cubes, cylinders and spheres. Pictograms and cartograms. The diagrams that are usually used to represent categorical data are:

5. These are the most commonly used diagrams. Horizontal or vertical lines or bars with their lengths proportional to the magnitude of the observations corresponding to each category constitute this diagram. Bars are preffered to lines as their thickness attracts the attention. Bars are drawn with the same width and at equal distances This type of diagram is called a bar diagram. ONE DIMENSIONAL DIAGRAMS

6. Simple bar diagrams Sub divided or component bar diagrams Percentage bar diagrams Multiple bar diagrams Deviation bar diagrams BAR DIAGRAMS ARE OF VARIOUS TYPES:

7. Horizontal or vertical bars with the same width, drawn with their bases on the same horizontal or vertical line with equal gaps in between length proportional to the magnitude of the observations constitute a bar diagram. This diagram is used when the data is in the form of observations corresponding to different categories. SIMPLE BAR DIAGRAM

8. Eg : Represent the information in the following table by a simple bar diagram Average yield of rice in kgs per hectre in various countries Country India U.SA. Italy Egypt Japan Yield in kgs per hectre 728 1469 2903 2153 2276

9. U sed when the observations corresponding to the various categories have different components When comparison of the component parts is important. Simple bar diagram is drawn first with the length of the bars proportional to the totals of the component parts. S ubdivided into parts of length proportional to the component magnitudes. Each part given a different color or shading. Eg : The growth of production of fish for the period 1996-97 to 2002-03 is given below: SUB DIVIDED OR COMPONENT BAR DIAGRAM

10. Year Marine Inland Total(lakh tonnes ) 1996-97 5.34 2.18 7.52 1997-98 8.80 2.80 11.60 1998-99 10.86 6.70 17.56 1999-00 15.55 8.87 24.42 2000-01 16.98 11.03 28.01 2001-02 17.16 11.60 28.76 2002-03 12.47 8.42 20.89

11. This is a modification of the component bar diagram. It is used when comparison of the component is thought to be more important. Component parts are expressed as the percentage of the total Component bar diagram is drawn with all bars having equal length. PERCENTAGE BAR DIAGRAMS

12. Eg : percentage expenditure on various items of the 3 families Components Family-1 Family-2 Family-3 Food 57.3 53.5 58.0 Clothing 10.7 11.0 12.0 Rent 13.3 13.5 8.2 Others 18.7 22.0 21.8

13. This diagrams are used for representing two or more interrelated data, for facilitating comparison. MULTIPLE BAR DIAGRAMS

14. Eg : Direct and Indirect taxes levied in India in 4 years Year Direct taxes( in crores of Rs .) Indirect taxes( in crores of Rs .) 1972 1200 2300 1975 2250 4100 1978 2500 6300 1981 3500 10000

15. This diagram is usually used to represent net quantities, like net profit, balance payable, deficit or excess etc. As the observations may be positive or negative, the basic line is usually drawn in the middle of the paper horizontally. Positive values are indicated by bars of proportional length, drawn above the horizontal line. Negative values by bars of proportional length drawn below the horizontal line. DEVIATION BAR DIAGRAMS

16. Eg : Profit and loss statement of a company for 4 years Year 1976 1977 1978 1979 Profit(millions of Rs .) 10 3 -5 -8

17. INTERPRETATION OF BAR DIAGRAM

18. From the bar diagram, we can interpret/infer: When to visit crete Which is the best month based on temperature Which is the hottest / coolest month Contd …

19. You can see that the temperature in january is 22ºC and then it rises to 40ºC in may. You would need to have an idea what these temperatures mean and can then decide what would be best for you. You might be decide that temperature above 26ºC would be too hot for you. You would then go on holiday in January or February, because the weather will be pleasant but not too hot. C ontd …