A supervisor records the repair cost for 17 randomly selected stereos. A sample mean of $66.34 and standard deviation of $15.22 are subsequently computed. Determine the 80% confidence interval for the mean repair cost for the stereos. Assume the population is approximately normal. Find the critical value that should be used in constructing the confidence interval. A supervisor records the repair cost for 17 randomly selected stereos. A sample mean of $66.34 and standard deviation of $15.22 are subsequently computed. Determine the 80 % confidence interval for the mean repair cost for the stereos. Assume the population is approximately normal. Construct the 80% confidence interval.