[Rd] anova and intercept

[peter dalgaard]

Yes, that works fine too. It likely depends on what you want to show and to whom. The audience might be ready to see the equivalence between t-tests and anova(lm(...)) but not yet prepared for variance components.

- Peter

> On 27 Dec 2022, at 18:55 , Greg Snow <538280 using gmail.com> wrote:
> 
> 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
>> 
>> ______________________________________________
>> R-devel using r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> 
> 
> -- 
> Gregory (Greg) L. Snow Ph.D.
> 538280 using gmail.com

-- 
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