Pilots’ mental efforts and a one-way withingroups ANOVA: Researchers examined the amount of mental effort that participants felt they were expending on a cognitively complex task, piloting an unmanned air vehicle (UAV) (Ayaz, Shewokis, Bunce, Izzetoglu, Willems, & Onaral, 2012). The researchers used the Task Load Index (TLX), a measure that assesses participants’ perception of their mental effort following a series of approach and landing tasks in simulated UAV tasks. They wondered whether expertise would have an effect on perceptions of mental effort. In the results section, the researchers reported the results of their analyses, a series of one-way repeated measures ANOVA. “The results indicated a significant main effect of practice level (beginner/intermediate/ advanced conditions) for mental demand (F (2, 8) = 17.87, p < 0.01, η² = 0.817), effort (F (2, 8) = 16.32, p < 0.01, η² = 0.803), and frustration (F (2, 8) = 8.60, p < 0.01, η² = 0.682).” They went on to explain that mental demand, effort, and frustration all tended to decrease with expertise.

a. What is the independent variable in this study?

b. What are the dependent variables in this study?

c. Explain why the researchers were able to use a oneway within-groups ANOVA in this situation.

d. η² is roughly equivalent to R². How large are each of these effects, based on Cohen’s conventions?

e. The researchers drew a specific conclusion beyond that there was some difference, on average, in the dependent variables, depending on the particular levels of the independent variable. What additional test were they likely to have conducted? Explain your answer.