The lengths of nails produced by a machine are known to be distributed normally with mean u mm and standard deviation 0.7 mm. The lengths, in mm, of a random sample of 5 nails are 107.29, 106.56,...

The lengths of nails produced by a machine are known to be distributed normally

with mean u mm and standard deviation 0.7 mm. The lengths, in mm, of a random sample of 5 nails are 107.29, 106.56, 105.94, 106.99, 106.47. Calculate

the 80% confidence interval for u .