What Type of Test for Population Means Should Be Performed

Multiple Choice

What type of test for population means should be performed when employees are first tested, trained, and then retested?

A) A z test under independent sampling with known population variances.
B) A t test under independent sampling with unknown but equal population variances.
C) A t test under dependent sampling.
D) A t test under independent sampling with unknown and unequal population variances.