The lengths of the leaves of a particular type of tree are normally distributed with mean \(\mu \mathrm{cm}\). The lengths, \(x \mathrm{~cm}\), of a random sample of 12 leaves of this type are recorded. The results are summarised as follows.
\(\sum x=91.2 \quad \sum x^{2}=695.8\)

Find a \(95 \%\) confidence interval for \(\mu\).