Answer:
(a) The sampling distribution of
= Population mean = 79
(b) P (
greater than 81.2 ) = 0.1357
(c) P (
less than or equals 74.4 ) = .0107
(d) P (77.6 less than
less than 83.2 ) = .7401
Step-by-step explanation:
Given -
Sample size ( n ) = 81
Population mean
= 79
Standard deviation
= 18
(a) Describe the sampling distribution of 
For large sample using central limit theorem
the sampling distribution of
= Population mean = 79
(b) What is Upper P (
greater than 81.2 ) =
= 
= 
= 
= 1 - .8643 =
= 0.1357
(c) What is Upper P (
less than or equals 74.4 ) =
= 
= 
= .0107
(d) What is Upper P (77.6 less than
less than 83.2 ) =
= 
= 
= 
= 0.9821 - .2420
= 0.7401