4. A population has a standard deviation of o=18.

On average, how much difference should exist between the population mean and the sample mean for n=4 scores randomly selected from the population? ( _____ points).

On average, how much difference should exist for a random sample of n=9 scores?

(____ points).

On average, how much difference should exist for a random sample of n=36 scores?

(______ points).