Basic Statistics and Data Analysis

Lecture notes, MCQS of Statistics

Category: Chart and Graphics

Pie Chart |Visual display of categorical data

Pie Chart

A pie chart is a way of summarizing a set of categorical data. It is a circle which is divided into segments/sectors. Each segment represents a particular category. The area of each segment is proportional to the number of cases in that category. It is useful way of displaying the data where division of a whole into component parts needs to be presented. It can also be used to compare such divisions at different times.

Pie chart is constructed by constructed by dividing the total angle of a circle of 360 degrees into different components. The angle A for each sector is obtained by the relation:

$A=\frac{Component Part}{Total}\times 360$

Each sector is shaded with different colour or marks so that they look separate from each other.

Example

Make an appropriate chart for the data are available regarding total production of urea fertilizer and its use on different crops. Let total production of urea is about 200 thousand (kg) and its consumption for different crops wheat, sugarcane, maize, and lentils is 75, 80, 30 and 15 thousands (kg) respectively.

Solution:

The appropriate diagram seems to be a pie chart because we have to present a whole into 4 component parts. To construct a pie chart, we calculate the proportionate arc of circle, i.e.

Crops

Fertilizer (000 kg)

Proportionate arc of the circle

Wheat

75

 $\frac{75}{200}\times 360=135$

Sugarcane

80

  $\frac{80}{200}\times 360=144$

Maize

30

  $\frac{30}{200}\times 360=54$

Lentils

15

  $\frac{15}{200}\times 360=27$

Total

200

360

Now draw a circle of an appropriate radius, make the angles clockwise or anticlockwise with the help of protractor or any other device. For wheat make an angle of 135 degrees, for sugarcane an angle of a44 degrees, for maize, an angle of 54 degrees and for lentils an angle of 27 degrees and hence the circular region is divided into 4 sectors. Now shade each of the sectors with different colour or mark so that they look different from each other. The pie chart of the above data is

pie chart for crops data

pie chart for crops data

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