A sample survey of 54 discounted brokers showed that the mean price charged for a trade of 100 shares at $50 per share was $33.77. The survey is conducted annually. With the historic data available, assume a known population std. 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 charged by discount brokers for a trade of 100 shares at $50 per share?