EXAMPLE 12.5

Are the standard deviations equal? In the Facebook friends study, there are I = 5 groups and the sample standard deviations are s₁ = 1.00, s₂ = 0.85, s₃ = 1.07, s₄ = 1.43, and s₅ = 1.02. Because the largest standard deviation (1.43) is less than twice the smallest (2 × 0.85 = 1.70), our rule indicates that we can use the assumption of equal population standard deviations.