SOLUTION: A random sample of 90 group leaders, supervisors, and similar personnel revealed that a person spent an average 5.5 years on the job before being promoted. The population standard

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Question 1191440: A random sample of 90 group leaders, supervisors, and similar personnel revealed that a person spent an average 5.5 years on the job before being promoted. The population standard deviation was 1.8 years. Using the 0.95 degree of confidence, what is the confidence interval for the population mean?
A. 6.99 and 7.99 B. 4.15 and 7.15 C. 5.13 and 5.87 D. 6.49 and 7.49
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
half-interval is z(0.975)*sigma/sqrt(n)
=1.96*1.8/sqrt(90)
=0.37
interval is (5.13, 5.87)
C