You are given the sample mean and the sample standard deviation. Assume the population is normally distributed and use the t-distribution to find the margin of error and construct a 95% confidence interval for the population mean Mobile Device Repair Costs In a random sample of 12 mobile devices, the mean repair cost was $90.42 and the standard deviation was $33.61. (a) Use the t-distribution to find the margin of error: S= (b) Construct a 95% confidence interval for the population mean. Cl Check