Question

A study of the career paths of hotel general managers sent questionnaires to a random sample of 106 hotels belonging to major U.S. hotel chains. The average time these 106 general managers had spent with their current company was 9.54 years. (Take it as known that the standard deviation of time with the company for all general managers is 3.9 years.)

(a) Find the bound for a 95% confidence interval to estimate the mean time a general manager had spent with their current company:  years

(b) Find the bound for a 99% confidence interval to estimate the mean time a general manager had spent with their current company:  years

(c) In general, increasing the confidence level  the bound of the confidence interval. (Enter: ''DECREASES'', ''DOES NOT CHANGE'' or ''INCREASES'', without the quotes.)

Answer 1

a)

95% confidence interval =8.80 ; 10.28

b)

for 99 % CI value of z=				2.58
margin of error E=z*std error                            =				0.977
lower confidence bound=sample mean-margin of error=				8.563
Upper confidence bound=sample mean +margin of error=				10.517

99% confidence interval bound for mean =8.56 ; 10.52

c)

'INCREASES