2 Karim has noted the lifespans, in weeks, of a large random sample of certain insects. He carries out a test, at the \(1 \%\) significance level, for the population mean, \(\mu\). Karim's null hypothesis is \(\mu = 6.4\).
- Given that Karim's test is two-tail, state the alternative hypothesis.
Karim finds that the value of the test statistic is \(z = 2.43\). - Explain what conclusion he should draw.
- Explain briefly when a one-tail test is appropriate, rather than a two-tail test.