# 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 8 pumpkins whose mass is between 6 and 9 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, 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 0 to 250 using bins with a width of 50, we can fit all of the data in 5 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.
Driving distance (in meters)Data pointsNumber of drives
0-49231
50-99781
100-149130, comma, 1472
150-199156, comma, 177, comma, 1843
200-2492131
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.
Want to learn more about making histograms? Check out this video.
Want to try some problems like this? Check out this exercise.