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Margin of Error

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The director of admissions has had questions from potential freshmen regarding the average price of textbooks per semester. In order to make an informed estimate of this cost, he selected a sample of 100 students and recorded their text book expenses for the most recent semester. He found a sample mean of $391.52. He assumes that the standard deviation of semester costs here is the same as the national (at $43.70).

a. What should he report as the average cost, if he wants to be 80% confident of his answer?

b. Is the sample mean here the same as the nationally reported average of $401.86? Use a 20% level of significance.

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Dear student, please refer to the attachment for the solution. Thank You.

Formula: n = [((Z_a/2)sigma)/E]2

where, n = sample size
(Z_a/2) = critical value
sigma = ...

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