Mean, Variance, and Standard Deviation for Grouped Data

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

2. Table 3.8 (p. 94)

3. Table 3.9 (p. 95)

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

5. Table 3.9 (p. 95) µ = 21.40 minutes

6. Table 3.10 (p. 95)

7. Table 3.11 (p. 96) x = 16.64 orders

8. Variance and Standard Deviation for Grouped Data • Start with variance. • Population Variance: σ2= ∑f (m- µ)2 N • Sample Variance: S2 = ∑f (m- x)2 n – 1 • For Standard Deviation, take square root of Variance.

9. Table 3.13 (p. 98) x = 16.64 orders S2 = 7.5820 orders S = 2.75 orders