EC321 Assignment 1 Due on 9/13/16 Name:
1. Missy Walters owns a mail-order business specializing in baby clothes. Missy is confident the dollar
amounts of all her orders are normally distributed. Assume all orders she receives are from a population
with mean and standard deviation are $249 and $46 respectively. (30pts, each part receives equal points.)
a. Describe the sampling distribution of
X
, where
X
is the mean dollar–amount of an order for a
sample of 30 orders. What happens to the sampling distribution of
X
when the sample size is
increased from 30 to 90?
b. What is the probability that a simple random sample of 30 orders will provide an estimate of the
population mean dollar-amount of an order that is within plus or minus $10 of the actual population
mean?
