I have generated data to understand a (repeated measures) 2x2 Anova better, however the results leave me baffled. The data is really simple: I am assuming I have 30 subjects, I am assuming that there are two medical tests, one in body region A, and one in body region B. I have created now the data as follows:
- Test1, region A: normal vector with mean 0.5 and standardeviation of 0.2
Test1, region B: normal vector with mean -0.5 and standardeviation of 0.2
Test2, region A: normal vector with mean -0.5 and standardeviation of 0.2
- Test2, region B: normal vector with mean 0.5 and standardeviation of 0.2
This is quite observations we really have: Test1 shows excitation of some substance in region A but inhibition in region B, while Test2 shows excitation of some other substance in region B but inhibition in region A.
Now the results of the ANOVA does show significant interaction of test and body region, however there is no significant main effect of region (p=0.86) - how can that be...? For both tests, the regions have clearly different measurement values. Help appreciated