A machine cuts steel to length for nails. The mean length of a
nail is 43 millimeters. There is concern that the settings of the
machine producing the nails have changed. To test the claim, 12
nails (n = 12) were sampled. The mean of the sample is 41.5 and the
standard deviation 1.784. To decide if the sample data support the
claim that the mean length is 43 millimeters, state your decision
in terms of the null hypothesis. Use a 0.02 level of
significance.