Question

A friend has performed a significance test of the null hypothesis that two means are equal. His report states that the null hypothesis is rejected in favor of the alternative that the first mean is larger than the second. In a presentation on his work, he notes that the first sample mean was larger than the second mean and this is why he chose this particular one-sided alternative.

Answer 1

We should only choose a one-sided alternative if we have some reason to expect a specific directional outcome before looking at the sample results

Explanation:

Wrong procedure applied by my friend, he use one sided hypothesis instead of two sided.