Oven thermostats were tested by setting them to 350 F and measuring actual temperature of oven. In a sample of 67 thermostats, the average temperature was 348.2 F and the standard deviation was 5.1 F.
1. Determine a 90% confidence interval for mean oven temperature.
2. Determine a 95% confidence interval for mean oven temperature.
3. Compute the confidence level of the interval (347.5, 348.9)
4. How many thermostats should be sampled so that 90% confidence interval specifies the mean to within +- 0.8 F.
5. How many thermostats should be sampled so that 95% confidence interval specifies the mean to within +- 0.8 F.