a population has a mean of 100 and a standard deviation of 20. If you select a single score from this population, on average, how close would it be to the population mean?

Question

a  population has a mean of 100 and a standard deviation of 20. If you select a single score from this population, on average, how close would it be to the population mean?

phi · Answer

I think they want the expected value of | x - m |  where x is the single score and m is the mean

E( | x - m| ) 

this equals  E(x)- E(m)
E(x) is m,  and E(m) (m is constant) is m
so you get m-m = 0