3 A machine produces circular metal discs whose radii have a normal distribution with mean \(\mu \mathrm { cm }\). A random sample of five discs is selected and their radii, in cm, are as follows.
$$\begin{array} { l l l l l }
6.47 & 6.52 & 6.46 & 6.47 & 6.51
\end{array}$$
- Calculate a \(95 \%\) confidence interval for \(\mu\).
- Hence state a 95\% confidence interval for the mean circumference of a disc.