Range

To calculate the range, subtract the smallest value from the largest. For the values 3, 5, 5, 7 and 10, the range is 10 minus 3, which is 7.

The range gives a quick sense of spread. For example, if a share's price moved between 42 and 58 over a year, its trading range was 16. If a company's monthly sales varied between 80,000 and 150,000, the range of 70,000 shows how much they fluctuated.

The range is easy to understand, but it has significant limitations. It depends only on the two most extreme values and ignores everything in between. A single unusual value, or outlier, can make the range very large even if all other values are close together. It also tends to increase as more data are collected, simply because more extreme values are likely to appear.

For these reasons, statisticians often use other measures of spread alongside or instead of the range, such as the interquartile range, which covers the middle 50% of the data, the variance and the standard deviation.