The monthly closing stock prices (rounded to the nearest dollar) for Panera Bread Co. for the first six months of 2010 are reported in the following table.

a. Calculate the sample mean and the sample standard deviation.

b. Compute the 90% confidence interval of the mean stock price of Panera Bread Co., assuming that the stock price is normally distributed.

c. What happens to the margin of error if a higher confidence level is used for the interval estimate? P-69

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Month January 2010 February 2010 March 2010 Closing Stock Price $71 73 76 78 May 2010 81 June 2010 75 April 2010