Question

How much experience do supply-chain transportation managers have in their field? Suppose in an effort to estimate this, 41 supply-chain transportation managers are surveyed and asked how many years of managerial experience they have in transportation. Survey results (in years) are shown below. Use these data to construct a 99% confidence interval to estimate the mean number of years of experience in transportation. Assume that years of experience in transportation is normally distributed in the population. 5 8 10 21 20 25 14 6 19 3 1 9 11 2 3 13 2 4 9 4 5 4 21 7 6 3 28 17 31 2 25 8 13 17 27 7 3 15 4 18 6 Appendix A Statistical Tables (Round the intermediate values to 3 decimal places. Round your answers to 3 decimal places.)

_______≤ μ ≤_________

Answer 1

	x	(X-Xbar)^2
	5	37.47829	Mean(X)=Xbar=sum(d)/n	11.121951
	8	9.746579	standard deviation(sd)=sqrt(sum(X-Xbar)^2/n-1)	8.4207931
	10	1.258775	n	41
	21	97.57585	for 90 % confidence level with degree of freedom (n-1)=7
	20	78.81975	\alpha=1-c%=1-0.99=0.01	0.01
	25	192.6002	degrees of freedom (n-1)	40
	14	8.283165	t=critical value at 99 % with (n-1) degree of freedom	2.7044593
	6	26.23438	Margin of error =t*s/sqrt(n)	3.5566531
	19	62.06365	Lower limit =Xbar-ME	7.5652981
	3	65.96609	Upper limit =Xbar+ME	14.678604
	1	102.4539
	9	4.502677
	11	0.014872
	2	83.20999
	3	65.96609
	13	3.527067
	2	83.20999
	4	50.72219
	9	4.502677
	4	50.72219
	5	37.47829
	4	50.72219
	21	97.57585
	7	16.99048
	6	26.23438
	3	65.96609
	28	284.8685
	17	34.55146
	31	395.1368
	2	83.20999
	25	192.6002
	8	9.746579
	13	3.527067
	17	34.55146
	27	252.1124
	7	16.99048
	3	65.96609
	15	15.03926
	4	50.72219
	18	47.30756
	6	26.23438
sum	456	2836.39

#99 % CI interval for mean is

7.565 ≤ μ ≤ 14.676