EXAMPLE 3 Constructing bar graphs

Construct a frequency bar graph and a relative frequency bar graph for the distributions of app type in Tables 2 and 4.

Solution

The bar graphs are provided in Figure 1a and 1b. Across the horizontal axis are the five app type categories. Next, draw rectangles, the heights of which represent either the frequency or the relative frequency for that category represented on the vertical axis. For example, in Figure 1a, the first rectangle (Games) reaches a height of 7, while the second rectangle reaches only to 5. Note that the rectangles are of equal width, and none of them touch each other. Also notice that the two bar graphs are exactly alike, except for the scale indicated on the vertical axis. This is because we divide each frequency by the same number, the sample size, to get the relative frequency.