Standard Deviation

QUESTION 1

The labor relations manager of a large corporation wished to study the absenteeism among workers at the company’s central office during the last year. a random sample of 25 workers revealed the following: an average of 9.7 days; a standard deviation of 4.0 days; and 12 employees were absent more than 10 days. In estimating the 95% confidence interval estimate of the proportion of workers absent more than 10 days last year what is the upper limit of the confidence interval?

a. 516

b. 6445

c .284

d. 676

QUESTION 2

You are considering investing in a company. The company claims for the past few years the average monthly return on such an investment has been $870 with a standard deviation of $50. You sample 30 investors and determine the sample average return to be $855. Using a .05 level of significance you will test to determine if there is evidence that the true average return is different from $870. Is this a 1 or 2 tail test?

a. 1 tail

b. 2 tail

c. indeterminate

d. none of the above

QUESTION 3

You are considering investing in a company. The company claims for the past few years the average monthly return on such an investment has been $870 with a standard deviation of $50. You sample 30 investors and determine the sample average return to be $855. Using a .05 level of significance you will test to determine if there is evidence that the true average return is different from $870. What are your critical values?

a. +- 1.65

b. +- 2.045

c. +-1.96

d. +-1.65