Question

A random sample of 49 measurements from a population with population standard deviation σ1 = 4 had a sample mean of x1 = 11. An independent random sample of 64 measurements from a second population with population standard deviation σ2 = 5 had a sample mean of x2 = 14. Test the claim that the population means are different. Use level of significance 0.01. What distribution does the sample test statistic follow? Explain.

Answer 1

Reject H0 and conclude that population means are different.

Explanation:

H0: μ1 = μ2

H1: μ1 ≠ μ2

x1 = 11 ; σ1 = 4 ; n1 = 49

x2 = 14 ; σ2 = 5 ; n2 = 64

The test statistic :

(x1 - x2) / sqrt[(σ1²/n1 + σ2²/n2)]

Test statistic :

(11 - 14) / sqrt[(4²/49 + 5²/64)]

Test statistic :

-3 / √0.7171556

Test statistic = - 3.542

Using α = 0.01

The critical value Zα/2 ; Z0.01/2 = 2.58

Decison region :

Reject H0 : if Test statistic < Zcritical

Reject H0 : - 3.542 < - 2.58