Using a Histogram

According to their raw data, the following waiting periods (in minutes) were measured for users at registration: 10, 12, 15, 18, 23, 38, 45, 48, 50, 64, 68, 72, 75, 80, 81, 84, 85, 88, 98, 110, 125, 130, 135, and 140. The team counted the number of data points in the series, and it is 24.

To organize their data, they first determine the range of the data, which is the difference between the highest and lowest data points: 140-10=130.

Next, they decide on the number of categories they will use to group the data. The manager and the team have 24 data points, so they decide to create 5 categories.

They determine the interval of the categories by dividing the range by the number of categories: 130/5=26 minutes (rounded to 30 minutes).

They determine the range of each interval by starting at 0 and adding the interval each time: 30, 60, 90, 120, 150. So the first interval will be 0-30, the second 31-60, and so on.

Now they look at their data and see how many times they observed data points in each interval. Then they construct what is called a frequency table:

Frequency Table for Waiting Time Data

Waiting Time in Minutes	Number of Users	Percentage
0-30	5	21%
31-60	4	17%
61-90	9	37%
91-120	2	8%
121-150	4	17%
Total	24	100%

Next, to create the histogram, the team draws a horizontal axis and vertical axis: the horizontal axis (x), represents waiting time in minutes, and the vertical axis (y) represents the number of users.

For each data category, they draw a rectangle. The height of the rectangle represents the observed number of users in each category. Here is the histogram they create:

By looking at the data in a histogram, it is easy to see that the majority of users wait from 61 to 90 minutes for registration.