1 Suppose that a random sample of size 81 is to be selected

1. Suppose that a random sample of size 81 is to be selected from a population with mean 30 and standard deviation 9.

a. What is the mean and standard deviation of sample mean x ?

b. What is the probability that the sample mean for sample size of 81 will be between 28 and 32?

c. What is the probability that the sample mean for sample size of 81 will be greater than 29?

a) E(xbar)=30

SE(Xbar)=sd/sqrt(n)=9/9=1

b) The distirbution is still normal so we use excel for calclaulting the probability

0.97725-0.02275=0.9545

c) 1-0.1586=0.8413