# A sample survey of 54 discount brokers showed that the mean price

July 3, 2016

Question
1. A sample survey of 54 discount brokers showed that the mean price charged for a trade of
100 shares at \$50 per share was \$33.77 (AAII Journal, February 2006). The survey is conducted
annually. With the historical data available, assume a known population standard
deviation of \$15.
a. Using the sample data, what is the margin of error associated with a 95% confidence
interval?
b. Develop a 95% confidence interval for the mean price charged by discount brokers for
a trade of 100 shares at \$50 per share.
2.. A survey conducted by the American Automobile Association showed that a family of four
spends an average of \$215.60 per day while on vacation. Suppose a sample of 64 families
of four vacationing at Niagara Falls resulted in a sample mean of \$252.45 per day and a
sample standard deviation of \$74.50.
a. Develop a 95% confidence interval estimate of the mean amount spent per day by a
family of four visiting Niagara Falls.
b. Based on the confidence interval from part (a), does it appear that the population mean
amount spent per day by families visiting Niagara Falls differs from the mean reported
by the American Automobile Association? Explain.