[R] R ANOVA gives diferent results than SPSS

Greg Snow Greg.Snow at imail.org
Thu Feb 11 19:45:03 CET 2010

A couple of possibilities:

The data is not the same, e.g. something in the file was interpreted differently by the 2 programs, one of the programs may have stopped reading at an unrecognized value, while the other skipped it and went on.  Or it used to be common to encode missing values as -999, if one program recognizes that as missing, but you did not tell the other one too, then it could treat that as a legitimate value.

The model is not the same, e.g. one program may be interpreting your grouping variable as a continuous variable and the other as categorical, which would result in 2 very different models and outcomes.

If you show us your data/code/output as has been requested, then we may be able to tell which it is.  Without that information you are expecting either R or the members of the list to read your mind.  I keep making notes to my future self to use the timetravel package (not written yet, that's why I need my future self to use it) to send a copy of the esp package (also not written yet) back in time to me so I can use it for situations like this.  But so far that has not worked (maybe my future self is even more lazy than my present self, or my near future self does something to offend my far future self enough that he is unwilling to do this small favor for my current past self, darn, either way means I should probably do better on the diet/exercise).  

The short version of the above rambling is that we want to help, but cannot help you until you help us to help you.  Show us your data/code/output (or data/code/output for simulated/example data if you can't show your real data).

Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Protzko
> Sent: Thursday, February 11, 2010 9:38 AM
> To: r-help at r-project.org
> Subject: Re: [R] R ANOVA gives diferent results than SPSS
> a one-way ANOVA should be a one-way ANOVA I guess, model is simple
> enough I
> thought.  The F value seems pretty clear, I'm doing nothing fancy here,
> just
> trying to figure out how to do in R what I'm doing in SPSS.
> --
> View this message in context: http://n4.nabble.com/R-ANOVA-gives-
> diferent-results-than-SPSS-tp1477322p1477468.html
> Sent from the R help mailing list archive at Nabble.com.
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