Chapter 3 - Section 3.3 - Mean, Variance, and Standard Deviation for Grouped Data - Exercises - Page 102: 3.47

mean = 8.85 variance = 12.5775 standard deviation = 3.5465

$Mean = μ =(∑mf)/N = [(3\times5)+(6\times9)+(9\times14)+(12\times7)+(15\times5)]\div5 =(15+54+126+84+75)\div40 =8.85 $ $Variance =σ^2 =(∑m^2 f-(〖(∑mf)〗^2/N))/N = \frac{3636- (125316\div40)}{40} =(3636-3132.9)\div40 =12.5775$ $Standard Deviation = \sqrt 12.5775= 3.5465$