I have similar questions like this in my homework(evens) so i decided to ask if someone can show me how to do this odd one...I missed class because my little girl was sick but I got the assignment and I wrote down the answer from the back of the book. The book is not really helpful and any help will be appreciated.

A population with a mean 1,250 and standard deviation of 400 is known to be highly skewed to the right. If a random sample of 64 items is selected from the population, what is the probability that the sample mean will be less than 1,325.

The answer is:

From a standard normal table, the probability associated with z-1.50=0.4332

therefore, P(x<1325)=P(z<1.5)=0.5+0.4332=0.9332