A survey of 25 randomly selected customers found the ages shown​(in years). The mean is 31.96 years and the standard deviation is10.12 years.
​a) Construct a 95​% confidence interval for the mean age ofall​ customers, assuming that the assumptions and conditions forthe confidence interval have been met.
​b) How large is the margin of​ error?
​c) How would the confidence interval change if you had assumedthat the standard deviation was known to be 11.0 ​years?
