The monthly closing stock prices (rounded to the nearest dollar) for Panera Brea

Question

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. Use Table 2.

Calculate the sample mean and the sample standard deviation. (Round intermediate calculations to 4 decimal places and "Sample mean" and "Sample standard deviation" to 2 decimal places.)

Compute the 95% confidence interval for the mean stock price of Panera Bread Co., assuming that the stock price is normally distributed. (Round "t" value to 3 decimal places and final answers to 2 decimal places.)

What happens to the margin of error if a higher confidence level is used for the interval estimate?

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. Use Table 2.

Explanation / Answer

a)
Sample mean = 54.67
Sample standard deviation = 3.01

b)
t value for 95% CI = 2.571
CI = mean + /- t * ( s / sqrt(n))
= 54.67 +/- 2.571 * ( 3.01 / sqrt(6))
= (51.509,57.830)

c) The margin of error increases as the confidence level increases.

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