9 A random sample of 8 observations of a normal random variable \(X\) gave the following summarised data, where \(\bar { x }\) denotes the sample mean. $$\Sigma x = 42.5 \quad \Sigma ( x - \bar { x } ) ^ { 2 } = 15.519$$ Test, at the \(5 \%\) significance level, whether the population mean of \(X\) is greater than 4.5. Calculate a 95\% confidence interval for the population mean of \(X\).