3 From previous years' observations, the lengths of salmon in a river were found to be normally distributed with mean 65 cm . A researcher suspects that pollution in water is restricting growth. To test this theory, she measures the length \(x \mathrm {~cm}\) of a random sample of \(n\) salmon and calculates that \(\bar { x } = 64.3\) and \(s = 4.9\), where \(s ^ { 2 }\) is the unbiased estimate of the population variance. She then carries out an appropriate hypothesis test.

1. Her test statistic \(z\) has a value of - 1.807 correct to 3 decimal places. Calculate the value of \(n\).
2. Using this test statistic, carry out the hypothesis test at the \(5 \%\) level of significance and state what her conclusion should be.