Re: [R] lm and anova

From: Paul Chatfield <p.s.chatfield_at_reading.ac.uk>
Date: Thu, 12 May 2011 06:30:59 -0700 (PDT)

anova uses sequential sums of squares (type 1), summary adjusted sums of squares (type 3)

Take for example the first line of each output. In summary this tests whether vole1 is needed ASSUMING volelag and year are already in the model (conclusion would then be: it isn't needed p=.89). Whereas in anova, it's testing do we need vole1 assuming nothing else is in the model (conclusion: vole1 is better than nothing. p=.0009).

anova assumes all terms above it are in the model but terms below it are not so volelag assumes vole1 is in the model but not year. You can see how anova changes but summary doesn't by varying the order you put them in.

so the final model I would fit here would probably end up being either year+volelag or just year,

HTH, Paul

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Received on Thu 12 May 2011 - 14:55:14 GMT

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