6th Grade Math Textbook, Fundamentals

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8-6

Histograms

Objective To make a frequency table using time intervals• To make a histogram from a

frequency table• To read a histogram

The tally chart below shows the results of a survey about
the number of customers at a store during each 2-hour
interval of the day from 10:00 a.m. to 8:00 p.m. How can
the results be shown in a graph?

To display the data shown in the tally chart visually in a graph,

first make a frequency table from the data. Then make a histogram.

A is a graph that shows frequencies of data within equal intervals.

Unlike the bars on a bar graph, the bars on a histogram are next to each

other without a gap, unless there is an interval that has a frequency of 0.

To make a frequency table, group the data into equal intervals. The intervals

will be shown on the horizontal axis of the histogram.

The frequency table below shows the number of customers that visit the

store in a 10-hour business day that is divided into 2-hour intervals.

The scale along the vertical axis of the histogram will include the

least data value and the greatest data value, and it will be divided

into equal intervals.

Using a scale with intervals of 2 would require a very tall graph.

Using a scale with intervals of 10 would not show the changes in

frequency clearly enough. Using intervals of 5 results in a scale

from 0 to 45.

To make a histogram:

Draw and label the horizontal axis and the vertical axis. The horizontal

axis shows the intervals; the vertical axis shows the frequencies.

Use the least and greatest values in the data to choose a sensible scale

for the frequencies. Use intervals of the same size throughout the scale.

histogram

Interval Frequency

10–11:59 42

12–1:59 35

2–3:59 24

4–5:59 17

6–7:59 19

Time Interval Number of Customers

10:00–11:59 A.M. 5 5 5 5 5 5 5 5 2

12:00–1:59 P.M. 5 5 5 5 5 5 5

2:00–3:59 P.M. 5 5 5 5 4

4:00–5:59 P.M. 5 5 5 2

6:00–7:59 P.M. 5 5 5 4