Definition: The range of a data set is the difference between its greatest value and its least value, and it measures how spread out the data are.
What is the range?
The range tells you the full width of the data. Subtract the minimum from the maximum.
How do you compute it?
Mathbot recorded the daily low temperatures in degrees Fahrenheit: 23, 31, 18, 27, 35, 29. The greatest is 35 and the least is 18. The range is 35 – 18 = 17 degrees.
What does it show?
A small range means the values cluster tightly. A large range signals big swings. Two sets can share the same mean but differ in range: 48, 50, 52 and 20, 50, 80 both average 50, yet their ranges are 4 and 60.
What are its limits?
The range uses only two values, so one outlier changes it a lot. Add a 90 to the temperatures above and the range becomes 72. That is why statisticians also use the interquartile range.
What mistake do students make?
Giving the endpoints, like 18 to 35, instead of a single number. The range is one number: 17.