It makes a difference whether or not we know the population variance because
A) we cannot deal with situations in which the population variance is not known.
B) we have to call the result t if the population variance is used.
C) we have to call the result z if the population variance is not used.
D) we have to call the result t if the sample variance is used.

Question

Quizplus · Accepted Answer

If we do not know the population variance, we have to use the sample variance instead. This means that we have to use a t-test instead of a z-test to make inferences about the population mean. Therefore, the correct choice is D.

It Makes a Difference Whether or Not We Know the Population