The length of steel bolts produced by a machine is normally distributed with a mean of 50.0 mm and a standard deviation of 0.8 mm.
Find the probability of a bolt being longer than 51.5 mm.
The technician suspects that the mean length of the bolts has changed.
Write down a null and alternative hypothesis for a two-tailed test.
A sample of 16 bolts is measured and the mean length is found to be 50.5 mm.
Test at the 10% significance level whether there is evidence that the mean length has changed.
