Accelerated lifetime tests are carried out for a batch of 200 thermocouples. The mean
lifetime is found to be 936 hours with a standard deviation of 28 hours. The smallest
and largest measurements in the sample are 860 and 1012 hours. The measurements
are divided into 9 data bins with boundaries at 859.5, 876.5, 893.5, 910.5, 927.5,
944.5, 961.5, 978.5, 995.5, and 1012.5. The measurement count in bin 1 from 869.5
to 886.5 days is 3 and the count in the other successive bins is 8, 27, 39, 46, 40, 24,
11, and 2. Apply the chi-squared test to see whether the measurements fit a Gaussian
distribution to (a) a 99% confidence level, (b) a 97.5% confidence level, and (c) a
95% confidence level.