Which of the following are always necessary assumptions for

Which of the following are always necessary assumptions for any of the 2-sample tests?

A. The two samples must always have at least 30 observations unless the data is normal.

B. The two samples must always be independent whether testing means or proportions.

C. The two samples must always have similar variances when testing means

D. All of the above are necessary.

E. None of the are always necessary.

Solution

Assumption A, B and C can be violated in different conditions for any of the 2-sample tests. For example little variation from normality does not effects the test.

So option E is correct.