1 A researcher wishes to investigate whether the mean height of a certain type of plant in one region is different from the mean height of this type of plant everywhere else. He takes a large random sample of plants from the region and finds the sample mean. He calculates the value of the test statistic, \(z\), and finds that \(z = 1.91\).

1. Explain briefly why the researcher should use a two-tail test.
2. Carry out the test at the \(4 \%\) significance level.