I have the following data:
- The same 25 subjects have participated in 3 tasks, once in city A and once in city B. So for each city, I have 75 datapoints - one datapoint for each task and each subject.
If I use a one-way repeated measures anova for city B to compare task performance of the subjects, there is no significant difference (p = 0.48).
Now when I use a two-way repeated measures Anova, taking data from both cities, the main effect of city proves significant (p < 0.0001). How is this possible? Can the main effect be so low even if task is only relevant in one of the two levels of the factor city (ie task performances are only significantly different in one of the cities)?