statistics
posted by Kim on .
A distribution of values follows a N(140,22) distribution. From this distribution you are drawing samples of size 12. Find the interval containing the middlemost 34% of the sample means. Round your values to 1 decimal place.

The interval = mean ± 17%.
Z = (scoremean)/SEm
SEm = SD/√(n1)
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion (.17) between Z score and mean. Insert the values in the first equation and calculate.