Oven thermostats were tested by setting them to 350? F and measuring the actual temperature of the..

Oven thermostats were tested by setting them to 350◦ F and measuring the actual temperature of the oven. In a sample of 67 thermostats, the average temperature was 348.2◦ F and the standard deviation was 5.1◦ F. a. Find a 90% confidence interval for the mean oven temperature. b. Find a 95% confidence interval for the mean oven temperature. c. What is the confidence level of the interval (347.5, 348.9)? d. How many thermostats must be sampled so that a 90% confidence interval specifies the mean to within ±0.8◦ F? e. How many thermostats must be sampled so that a 95% confidence interval specifies the mean to within ±0.8◦ F?