Chapter 14, Problem 14P

Most sports injuries are immediate and obvious, like a broken leg. However, some can be more subtle, like the neurological damage that may occur when soccer players repeatedly head a soccer ball. To examine effects of repeated heading. McAllister et al. (2012) examined a group of football and ice hockey players and a group of athletes in noncontact sports before and shortly after the season. The dependent variable was performance on a conceptual thinking task. Following are hypothetical data from an independent-measures study similar to the one by McAllister et al. The researchers measured conceptual thinking for contact and noncontact athletes at the beginning of their firs; season and for separate groups of athletes at the end of their second season.

a. Use a two-factor ANOVA with $\alpha =.05$ to evaluate the main effects and interaction.

b. Calculate the effects size $({\eta }^2)$ for the main effects and the interaction.

c. Briefly describe the outcome of the study.

		Factor B: Time
		Before the

First SeasonAfter the

Second Season

Factor A: Sport

Contact

Sport
   $n=20$

   $M=9$

   $T=180$

   $SS=380$
   $n=20$

   $M=4$

   $T=80$

   $SS=390$

Non-

contact

Sport
   $n=20$

   $M=9$

   $T=180$

   $SS=350$
   $n=20$

   $M=8$

   $T=160$

   $SS=400$

   ${\displaystyle \sum X^2}=6360$