Mean, Variance, and Standard Deviation for Grouped Data Section 3.3

Table 3.8 (p. 94)

Table 3.9 (p. 95)

Mean for Grouped Data Find midpoint for each class ( m ). Multiply m by frequency ( f ) of that class. Mean of Population: µ = ∑ m f N Mean of Sample: x = ∑ m f n

Table 3.9 (p. 95) µ = minutes

Table 3.10 (p. 95)

Table 3.11 (p. 96) x = orders

Variance and Standard Deviation for Grouped Data Start with variance. Population Variance: σ 2 = ∑ f ( m - µ) 2 N Sample Variance: S 2 = ∑ f ( m - x) 2 n – 1 For Standard Deviation, take square root of Variance.

Table 3.13 (p. 98) x = orders S 2 = orders S = 2.75 orders