6.5 6.6 6.7 6.8 7.1 7.3 7.4 7.7 7.7 7.7 B. The listed values are waiting times (

Question

6.5    6.6    6.7      6.8      7.1      7.3      7.4      7.7      7.7       7.7

B. The listed values are waiting times () of customers at theBank of Providence, where customers may enter any one of threedifferent lines that have formed at three teller windows. Constructa 95% confidence interval for the population standard deviation.

4.2 5.4 5.8      6.2      6.2      6.7      7.7      7.7      8.5      9.3       10.0

C.Interpret the results found in parts (a) and (b). Do theconfidence intervals suggest a difference in the variation amongwaiting times? Which arrangement seems better: the single linesystem or the multiple line system?

I have the answer, which is below, but I would like helpwith the solution

A.     0.33 min < <0.87 min

B.     1.25 min < < 3.3 min

C.     They do not overlap.

Explanation / Answer

A) mean of the given data = = 7.15 standard deviation of the given data = = 0.48 for 95% confidence, z = 1.96 hence confidence interval = ± z = 7.15 ±0.48 x 1.96 =( 6.2 , 8.09) B)mean of the given data = = 7.06 standard deviation of the given data = = 1.75 for 95% confidence, z = 1.96 hence confidence interval = ± z = 7.06 ±1.75 x 1.96 =( 3.63 , 10.49) C.     They do overlap.

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