Chapter 3 - Statistics for Describing, Exploring, and Comparing Data - 3-3 Measures of Variation - Basic Skills and Concepts - Page 108: 15

Variance:11.675. Standard deviation:3.417 Range:11.

By using the results from before: $\mu=6.5.$ Variance=$\frac{\sum (x-\mu)^2}{n}=\frac{(4-6.5)^2+(4-6.5)^2+...+(15-6.5)^2}{20}=11.675.$ Standard deviation=$\sqrt{variance}=\sqrt{11.675}=3.417$ Range=maximum value-minimum value=$15-4=11$.