6.53 What’s wrong? Here are several situations where there is an incorrect application of the ideas presented in this section. Write a short paragraph explaining what is wrong in each situation and why it is wrong.

1. 380

   (a) A significance test rejected the null hypothesis that the sample mean is equal to 500.

2. (b) A test preparation company wants to test that the average score of its students on the ACT is better than the national average score of 21.2. The company states its null hypothesis to be H₀: μ > 21.2.

3. (c) A study summary says that the results are statistically significant and the P-value is 0.98.

4. (d) The z test statistic is equal to 0.018. Because this is less than α = 0.05, the null hypothesis was rejected.