4 The lengths, in millimetres, of rods produced by a machine are normally distributed with mean \(\mu\) and standard deviation 0.9. A random sample of 75 rods produced by the machine has mean length 300.1 mm .
- Find a \(99 \%\) confidence interval for \(\mu\), giving your answer correct to 2 decimal places.
The manufacturer claims that the machine produces rods with mean length 300 mm . - Use the confidence interval found in part (i) to comment on this claim.