[R] R ANOVA gives diferent results than SPSS

[Peter Dalgaard]

Thomas Lumley wrote:
> On Thu, 11 Feb 2010, Protzko wrote:
> 
>>
>> I guess my subject says it all.  But I loaded a dataset in spss and
>> used the
>> foreign package to read and save it in R.  Running an anova (using the
>> aov
>> command) gives a different F and p value in R than it does in SPSS.  ANy
>> idea what is going on?
> 
> Yes. Either you specified a different model or different tests for the
> same model in the two systems, or you are interpreting the output
> incorrectly, or the results are different.

Also beware of unbalanced data sets, aov() will not handle Error() terms
properly in an unbalanced design, and in general tests will be order
dependent (type 1 tests in SAS terminology).

> 
> Without more detail it is hard to be sure, but the first two
> possibilities seem more likely.

Yes, many people on the list can probably spot the issue when seeing the
two anova tables.

> 
>         -thomas
> 
> Thomas Lumley            Assoc. Professor, Biostatistics
> tlumley at u.washington.edu    University of Washington, Seattle
> 
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