Chapter 3 - Section 3.2 - Assess Your Understanding - Vocabulary and Skill Building - Page 151: 8

The variance: $σ^2=64$ The standard deviation: $σ=8$

At first, let's evaluate the population mean: $μ=\frac{1+19+25+15+12+16+28+13+6}{9}=15$ Now, the variance: $σ^2=\frac{Σ(x_i-μ)^2}{n}=\frac{(1-15)^2+(19-15)^2+(25-15)^2+(15-15)^2+(12-15)^2+(16-15)^2+(28-15)^2+(13-15)^2+(6-15)^2}{9}=\frac{196+16+100+0+9+1+169+4+81}{9}=64$ The standard deviation: $σ=\sqrt {64}=8$