**Central tendency** is used to describe the middle of a data set.

The **median** and the **mode** are measures of central tendency.

**Spread** is used to describe how close the data points in a data

set are to each other. The **range** is a measure of spread.

- Median
- The median is the middle value in a data set when the values are listed from least to greatest.

- Mode
- The mode is the value that occurs the most times in the data set.

- Range
- The range is the difference between the highest and lowest values in the data set.

First, find the median.

The median is the middle value in the data set.

Write the numbers in order from least to greatest.

3, 7, 7, 7, 12, 12, 18, 19, 23

The middle value in the data set is 12.

3, 7, 7, 7, **12**, 12, 18, 19, 23

So, the median is 12.

Next, find the mode.

The mode is the value that occurs the most times in the data set.

In this data set, 3, 18, 19, and 23 each occur once, 12 occurs twice, and 7 occurs three times.

So, the mode is 7.

Then, find the range.

The range of a data set is the difference between the highest and lowest values.

In this data set, the lowest value is 3, and the highest value is 23.

Find the difference between 3 and 23.

So, the range is 20.