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A survey of 25randomly selected customers found the ages shown​ (in years). The mean is 32.88years...

A survey of 25randomly selected customers found the ages shown​ (in years). The mean is 32.88years and the standard deviation is10.67 years

.​a) Construct a80​%
confidence interval for the mean age of all​ customers, assuming that the assumptions and conditions for the confidence interval have been met.

​b) How large is the margin of​ error?

​c) How would the confidence interval change if you had assumed that the standard deviation was known to be

11.0​years?

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