Answer
Variance:12.3. Standard deviation:3.5 Range:11.
Work Step by Step
By using the results from before: $\mu=6.5.$ Variance=$\frac{\sum (x-\mu)^2}{n}=\frac{(4-6.5)^2+(4-6.5)^2+...+(15-6.5)^2}{20}=12.3.$ Standard deviation=$\sqrt{variance}=\sqrt{11.675}=3.5$ Range=maximum value-minimum value=$15-4=11$.
