I'm currently running a perception experiment:
- DV: error (this in degrees- how much an observer was away from the real answer)
- IV: the time bin (5 levels) in which the unique stimulus appeared
- IV2: True/False- whether the unique stimulus occurred before or after stimulus2.
- Covariate: Distance from the fixation point this stimulus appeared (continuous)
So, I have decided to use repeated measures ANCOVA since, all the observers were exposed to all 5 levels of the IV multiple times.
Currently I have written:
data.aov <-aov(error~(timebin*after*distance) + Error(subject/timebin*after*distance), d) summary(data.aov)
Is this the correct way to specify my repeated measures ANCOVA in R?
Also, I wanted to run this analysis in SPSS to check that I get the same results. However, SPSS doesn't like the format of my data.
For repeated measures analysis, the 5 bins should be in 5 different columns, but in my data file, they are all together under the same heading
How can I run the repeated measures ANCOVA in SPSS if my data are in long format?
Thanks everyone for great answers!
@Marcus, just one thing- regarding regression. If I were to use regression, would I be looking at trends? I am actually more interested in comparing bin 1 and bin 5. This is why I was going to use a t-test, but now it seems like I am using within-subjects anova.
Also, I've had a look at distance and (as you said) might not be a covariate, since it was randomised for every condition!
Then the codes should look like this?
data.aov <-aov(error~(timebin*after) + Error(subject/timebin*after), d) summary(data.aov)
But what is the difference between using
* and using
Should I use
* to get an interaction effect?