Representing data in a pie chart

10 months ago (Edited)

A pie chart is one of the tools used to present statistical data. Data in a pie chart is presented in a circle. Each item of data occupies a sector of the circle in relation to its size of frequency. The pie chart has the entire sector equal to 360^o which is the total of all the angles of a circle.

Calculating the size of each sector of the circle is not usually too difficult. To begin, you have to get a total of all the items in the circle. Then each item size is divided by the total or summation and then multiplied by 360^o. This is usually done in a table to make it comprehensive. After doing the calculation, then the summation of each angle of the sectors should be 360^o. Once this is gotten correctly, the pie chart could be drawn correctly.

Pie charts can be used to compare the proportion of a set of values in order to determine how large or small they are. For example, a pie chart could be used to represent the ages of students, the population distribution of a given area, the budget of a country and similar data as is needed.

Working with examples

Example 1: Below are the scores of 6 students in a mathematics test. (a) Represent the information in a pie chart.
(b) Calculate the percentage that goes to Paul.
(b) What percentage of the total goes to Mary?

Name of Student	Score
Mary	50
John	150
Eze	250
Kalu	40
Chinyere	50
Paul	60

Solution
First of all, we need to sum the total of their scores.
Total scores=70+45+40+80+35+50 = 320

Next, we need to divide each score by the total score and them multiply by 360^o. That will give the size of each sector in the pie chart.

Table of scores and sectors

Name of Student	Score	angle of sector (degrees)
Mary	50	(50/600)x360 = 30^o
John	150	(150/600)x360 = 90^o
Eze	250	(250/600)x360 = 150^o
Kalu	40	(40/600)x360 = 24^o
Chinyere	50	(50/600)x360 = 30^o
Paul	60	(60/600)x360 = 36^o
Total	600	360^o

Having calculated the sectors, I can now draw the pie chart. I will use an online tool to create the pie chart - https://www.meta-chart.com/pie#/display

created online

(b) Calculating the percentage that goes to Paul, we have:
Paul: (50/600)x100 = 10.0%

(c) Calculating the percentage of the total that goes to Mary, we have
Paul: (60/600)x100 = 8.3%

Conclusion

As you can see, it is easy to create a pie chart from the data given if you pay attention to the steps above. Remember to always run a total of the the figures given. Then try to know the size of each sector by dividing the figure for that sector by the total, then multiply by 360. This way, you could easily represent data of this nature in a pie chart.

We will see further examples in the next presentation.

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