Finding the frequency

Sometimes a histogram will already be drawn for us. We can then use this to find the frequency of each group, and hence the total frequency for the distribution.

This histogram is to show the number of books sold in a bookshop one Saturday.

Histogram labelled 'Frequency density (number of books per £)' on the y-axis and 'Price (P) in pounds (£)' on the x-axis.

To find the frequency of each group, we need to multiply the height of the bar by its width, because the area of each bar represents the frequency.

For the first bar, the height is 8 and the width is 5 so:

Frequency = 8 x 5 = 40

If we do the same for each bar, we get:

A table with four rows and two columns labelled 'Price (P) in pounds (£)' and 'Frequency' .

Question

This histogram shows information about the distances in metres that a number of people threw a ball.

Find the frequency of each group using the histogram.

Interpreting distributions from histograms

Frequency density

Histograms - Higher only – WJECFinding the frequency