# 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