confidence interval and Z

A local university administers a comprehensive examination to the candidates for B.S. degrees in Business Administration. Five examinations are selected at random and scored. The scores are shown below.

Grades
80
90
91
62
77

I am interested in the overall performance for all candidates of a B.S. degree. The population is therefore the theoretical distribution of their scores. Call the population mean μ. Compute a point estimate for μ - this is your best guess on the average performance for all candidates. Mean or μ is 80

What is a 95% confidence interval (interval estimate) for μ.
a. P[90.32 < μ<69.68] = .95
b. P[90.32 < μ<69.68] = .05
c. P[85.32 < μ<75.32] = .95
d. P[85.32 < μ<75.32] = .05

2. For confidence intervals (two tailed), the critical value of Z at 99.2% confidence (or the .008 significance) is
a. 2.65
b. 2.44
c. 2.41
d. 1.645

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