[R] lm and anova

[peter dalgaard]

On May 12, 2011, at 15:30 , Paul Chatfield wrote:

> anova uses sequential sums of squares (type 1),

Yes.

> summary adjusted sums of
> squares (type 3)

No. Type III SS is a considerably stranger beast. 

summary() looks at the s.e. of individual coefficients. For 1 DF effects, this is often equivalent to Type II tests (not III, except when they happens to be equal), except when looking at main effect terms in the presence of interactions (in which case things get parametrization-dependent.)

-- 
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com