Histograms review

Histograms

A histogram displays numerical data by grouping data into "bins" of equal width. Each bin is plotted as a bar whose height corresponds to how many data points are in that bin.

Bins are also sometimes called "intervals", "classes", or "buckets".

Reading a histogram

The heights of the bars tell us how many data points are in each bin.

For example, this histogram says that Leonard's patch has 8888 pumpkins whose mass is between 6666 and 9999 kilograms.

Want to learn more about reading histograms? Check out this video**.

Want to practice some more problems like this? Check out this exercise**.

Creating a histogram

Below are the lengths (in meters) of Luiza's 8 drives from the last time that she played golf.

23,78,130,147,156,177,184,21323, 78, 130, 147, 156, 177, 184, 21323,78,130,147,156,177,184,21323, comma, 78, comma, 130, comma, 147, comma, 156, comma, 177, comma, 184, comma, 213

Here's how to make a histogram of this data:

Step 1: Decide on the width of each bin. If we go from 0000 to 250250250250 using bins with a width of 50505050, we can fit all of the data in 5555 bins.

There is no strict rule on how many bins to use—we just avoid using too few or too many bins.

Step 2: Count how many data points fall in each bin.

Step 3: Scale the x-axis from 0 to 250 using intervals of width 50. Label the x-axis "driving distance (meters)".

Step 4: Scale the y-axis up to 3—or something just past it—since that will be the highest bar.

Step 5: Draw a bar for each interval so its height matches the number of drives in that interval.