Difference between one way ANOVA and within subjects ANOVA with one factor?

[jamie10]

Hi there,

Out of interest I set up tests to run both a between subjects one way ANOVA and a one factor, repeated measures ANOVA in SPSS.

There are 3 conditions and one DV (one way anova), or 1 group and 3 DVs (within subjects anova, 1 factor)

They produced different results.

I would have thought since they are simply testing the variances of a) the dependent variables of the a condition with three levels they would produce the same result.

Any idea why this doesn't happen?

Thanks for your help!

[mattc]

The one-way ANOVA assumes that the 3 conditons are independent, and the repeated measures ANOVA assumes that the conditions are dependent and each set of 3 come from the same subject. So your DFs are different, and the SS would be different as well.

It's a lot like running an independent samples t-test and a paried t-test on the same dataset. You'd have different results.

[jamie10]

Thanks Matt! Yes this makes sense, I had a sense that may be the case, just couldn't be certain. Appreciated!