Understanding the Mean Graphically: Four or more bars

In this lesson we understand the mean of a dataset using graphical method. Suppose we are given a bar graph showing four bars of data. Here we are required to find the mean of given data graphically.

Rules to find the mean graphically

In the bar graph we find the heights of the four bars.

The average or mean of these heights is found.

We then draw a fifth bar with the average height found in second step.

The height of this fifth bar gives the mean or average of given data set graphically.

The four bars in a bar graph have heights 14, 16, 18, and 22. What height a new bar should have so that it is the mean height of the four bars?

Solution

Step 1:

Heights of given bars 14, 16, 18 and 22

Step 2:

Mean height = $frac{(14 + 16 + 18 + 22)}{4} = frac{70}{4}$ = 17.5

So height of new bar = 17.5.

The four bars in a bar graph have heights 15, 16, 17 and 20. What height a new bar should have so that it is the mean height of the four bars?

Solution

Step 1:

Heights of given bars 15, 16, 17 and 20

Step 2:

Mean height = $frac{(15 + 16 + 17 + 20)}{4} = frac{68}{4}$ = 17

So height of new bar = 17