researcher was comparing motivation among participants randomly assigned to one of three varying methods to increase self-efficacy (i.e., belief in one's ability to succeed). The calculated effect size was 2 = .27. What can you conclude based on this effect size? a. The difference in mean motivation scores among the groups was significantly different. b. The difference in mean motivation scores among the groups was not significantly different. c. The groups differed by 0.27 standard deviations on average. d. The conditions of self-efficacy can explain 27% of the variance in motivation