Question

A study by M. Chen et al. titled "Heat Stress Evaluation and Worker Fatigue in a "Steel Plant" (American Industrial Hygiene Association, Vol. 64, pp.352-359) assesses fatigue in steelplant workers due to heat stress. Among other things, the researchers monitored the heart rates of a random sample of 29 casting workers. A hypothesis test is to be conducted to decide whether the mean post-work heart rate of casting workers exceeds the normal resting heart rate of 72 beats per minute (bpm)

Answer 1

a. Type I error (rejecting a null hypothesis when it is true).

b. Correct conclusion (reject a null hypothesis when it is false).

Explanation:

The question is incomplete:

Now suppose that the results of carrying out the hypothesis test lead to rejection of the null hypothesis.

Classify that conclusion by error type or as a correct decision if in fact:

a. the mean post-work heart rate of casting workers equals the normal resting heart rate of 72 bpm.

b. exceeds the normal resting heart rate of 72 bpm.

In case a, the conclusion is wrong and we have rejected a null hypothesis that is true. This is a Type I error, and it has a probability equal to the level of significance α.

In case b, the conclusion is correct, as the mean post-work heart rate indeed exceeds the normal resting heart rate of 72 bpm.