[Rd] anova and intercept

[Greg Snow]

Why compute the  differences manually when `aov` can do paired
comparisons on this data as is:

summary(aov(extra ~ factor(group) + Error(ID), data=sleep ))

gives the same F and P values

On Tue, Dec 27, 2022 at 3:32 AM Gabor Grothendieck
<ggrothendieck using gmail.com> wrote:
>
> Good idea.
>
> On Mon, Dec 26, 2022 at 12:59 PM peter dalgaard <pdalgd using gmail.com> wrote:
> >
> > My usual advice on getting nonstandard F tests out of anova() is to fit the models explicitly and compare.
> >
> > So how about this?
> >
> > fit1 <- lm(diff(extra,10) ~ 1, sleep)
> > fit0 <- update(fit1, ~ -1)
> > anova(fit0, fit1)
> >
> > -pd
> >
> > > On 26 Dec 2022, at 13:49 , Gabor Grothendieck <ggrothendieck using gmail.com> wrote:
> > >
> > > Suppose we want to perform a paired test using the sleep data frame
> > > with anova in R.  Then this works and gives the same p value as
> > > t.test(extra ~ group, sleep, paired = TRUE, var.equal = TRUE)
> > >
> > >   ones <- rep(1, 10)
> > >   anova(lm(diff(extra, 10) ~ ones + 0, sleep)
> > >
> > > This gives output but does not give an F test at all.
> > >
> > >   ones <- rep(1, 10)
> > >   anova(lm(diff(extra, 10) ~ 1, sleep)
> > >
> > > Maybe there should be some way to force an F test to be produced for
> > > the intercept in anova for consistency with t.test so that the second
> > > code can be used.
> > >
> > >
> > > --
> > > Statistics & Software Consulting
> > > GKX Group, GKX Associates Inc.
> > > tel: 1-877-GKX-GROUP
> > > email: ggrothendieck at gmail.com
> > >
> > > ______________________________________________
> > > R-devel using r-project.org mailing list
> > > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> > --
> > Peter Dalgaard, Professor,
> > Center for Statistics, Copenhagen Business School
> > Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> > Phone: (+45)38153501
> > Office: A 4.23
> > Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com
> >
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
>
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-- 
Gregory (Greg) L. Snow Ph.D.
538280 using gmail.com