Question: Question 8.70

The personnel director of a large corporation whishes to study absenteeism among clerical workers at the corporation’s central office during the year. A random sample of 25 clerical workers reveals the following:

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? Absenteeism: X = 9.7 days, S = 4.0 days

? 12 clerical workers were absent more than 10 days

? Construct a 95% confidence interval estimate for the mean number of absences for clerical workers during the year.

a. Construct a 95% confidence interval estimate for the population proportion of clerical workers absent more than 10 days during the year.

b. Suppose that the personnel director also wishes to take a survey in a branch office. Answer these questions:

c. What sample size is needed to have 95% confidence in estimating the population mean absenteeism to within 1.5 days if the population standard deviation is estimated to be 4.5 days.

d. How many clerical workers need to be selected to have 90% confidence in estimating the population proportion to within 0.075 if no previous estimate is available?

e. Based on © and (d), what sample size is needed if a single survey is being conducted?