# Answers to Test Yourself

Below are answers to the chapter Test Yourself feature.

**(1)** c** (2)** c** (3)** b **(4)** a **(5) **b **(6)** b **(7) **a **(8) **a** (9) **a **(10) **d** (11) **c** (12) **d** (13) **a** (14) **a** (15) **b** (16) **b **(17) **c **(18)** a **(19) **b **(20) **b **(21) **b **(22) **a (**23a) **He needs the mean score in the population when videos are not used. **(23b) **Using videos to illustrate concepts in class has no effect or decreases exam scores in the population of students.** (23c)** ~ 1.67 **(24) **The *t* score of 3.5 falls within the critical region, meaning we can reject the null hypothesis. The results suggest the instructor’s claim is accurate. **(25 a)** The population mean difference score is greater than zero between scores without the videos and scores with the videos. **(25 b)** The population mean difference score is less than or equal to zero. **(25 c)** *t _{crit }*= 1.671

**(25 d)**Yes, the videos seem to help. The

*t*score (4.92) is in the critical area. We can reject the null hypothesis. The results suggest videos help improve exam scores.

**(26)**Yes. The

*t*score (8.33) is in the critical area. We can reject the null hypothesis. The results suggest cellphone use decreases driving performance.

**(27a)**The null hypothesis tested in the analysis is that there is no mean difference between video discussion and no video discussion groups in the population. The alternative hypothesis is that is that there is a mean difference between video discussion and no video discussion groups in the population.

**(27b)**No answer needed.

**(27c)**The video discussion group had mean recognition accuracy of 72.7% (SD = 5.23), and the no video discussion group had a mean recognition accuracy of 82.4% (SD = 7.52). The test indicates that the no video discussion group has a significantly higher mean recognition score than the video discussion group,

*t*(18) = -3.35,

*p*= .004. Because the

*p*value of .004 is less than alpha (.05), we can conclude that the null hypothesis is false and that there is a difference between video and no video groups in the population.