Variable

A variable of a population has a mean of µ = 100 and a standard deviation of ? = 40.

(a) If a variable is normally distributed, identify the sampling distribution of the sample mean for
samples of size 20.
(b) Can you answer part (a) if the distribution of the variable under consideration is unknown? Explain
your answer.
(c) Can you answer part (a) if the distribution of the variable under consideration is unknown but the
sample size is 40 instead of 20? Why or why not?

how do you do a.) and is b.) no and c.) yes?

A) The distribution of the mean has µ = 100 and a standard deviation of \(\displaystyle \sigma = \frac{40}{\sqrt{20}}\)?

This should be VERY familiar. It is totally fair game on an exam.