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Suppose that the random variable X represents the amount of electrical energy used (in kwH) in a month for residents in Virginia. The following data (in kwH per month) were recorded from a random sample of 12 residents: 111 113 145 105 90 100 150 88 120 84 230 110 Using the data from the table and assuming that X approximately follows a normal distribution with o' = 1. (a) Construct a 95% confidence interval for the population mean /. (b) Suppose we don't know the population variance o'. Construct a 95% confidence interval for o