Psychomotor retardation scores for a particular group of manic depressive patients have approximately a normal distribution with a mean of 930 and a standard deviation of 130 A random sample of 20 patients from the group was selected, and their mean psychomotor retardation score was obtained a What...

Psychomotor retardation scores for a particular group of manic-depressive patients have approximately a normal distribution with a

Question:

Psychomotor retardation scores for a particular group of manic-depressive patients have approximately a normal with a mean of 930 and a standard deviation of 130. A random sample of 20 patients from the group was selected, and their mean psychomotor retardation score was obtained.
a. What is the probability that their mean score was between 900 and 960?
b. What is the probability that their mean score was greater than 960?
c. What is the 90th percentile of their mean scores?
Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...