Suppose That We Know That the Sample Mean Is 18

Multiple Choice

Suppose that we know that the sample mean is 18 and the population standard deviation is 3. We want to test the null hypothesis that the population mean is 20. In this situation we would

A) reject the null hypothesis at a = .05.
B) reject the null hypothesis at a = .01
C) retain the null hypothesis.
D) We cannot solve this problem without knowing the sample size.