Q.State, with a reason, whether each of the following calls for a one-tailed or a two-tailed test:

The wording of the alternative hypothesis is what decides the number of tails - 'different from' spreads the risk of a wrong rejection across both directions, while a directional claim like 'greater than' concentrates it in one. …

(a) The claim to be tested is whether the average life is different from 40,000 km - this allows for either an increase OR a decrease being of interest, so $H_1: \mu \neq 40{,}000$, and the critical region is split across both tails of the distribution. This is a two-tailed test. …

A common error is to decide one-tailed vs two-tailed based on the wording of H0 - it is always the wording of H1 (the specific direction of the claim being tested) that det …