Two independent samples of sizes 20 and 25 are randomly sele

Two independent samples of sizes 20 and 25 are randomly selected from two normal populations with equal variances. In order to test the difference between the population means, the test statistic is:

Solution

In order to test the difference between the population means, the test statistic is:

T test

because if we have a difference between population means we need to use t test no matther if we know the SD of population or not