[R] Getting Sphericity Tests for Within Subject Repeated Measure Anova (using "car" package)

[Mike Lawrence]

No luck as in...? What error did you encounter?

In your example data set, you only have 2 levels of each within-Ss
factor, in which case you shouldn't expect to obtain tests of
sphericity; as far as I understand it, sphericity necessarily holds
when for repeated measures with only 2 levels and tests are really
only possible for repeated measures with 3 or more levels.

I think it's analogous to how you don't need to test homogeneity of
variance when performing a paired t-test; the test ends up
representing the pairs as single distribution of difference scores
with a single variance.

Mike

On Mon, Nov 9, 2009 at 5:30 PM, Sergios (Sergey) Charntikov
<sergioschr at gmail.com> wrote:
> Tried EZanova, no luck with my particular dataset.
>
>
> Sincerely,
>
> Sergios Charntikov (Sergey), MA
>
> Behavioral Neuropharmacology Lab
> Department of Psychology
> University of Nebraska-Lincoln
> Lincoln, NE 68588-0308  USA
>
>
>
>
> On Mon, Nov 9, 2009 at 2:25 PM, Mike Lawrence <Mike.Lawrence at dal.ca> wrote:
>>
>> Have you tried ezANOVA from the ez pacakge? It attempts to provide a
>> simple user interface to car's ANOVA (and when that fails, aov).
>>
>> On Mon, Nov 9, 2009 at 1:44 PM, Sergios (Sergey) Charntikov
>> <sergioschr at gmail.com> wrote:
>> > Hello everyone,
>> >
>> > I am trying to do within subjects repeated measures anova followed by
>> > the
>> > test of sphericity (sample dataset below).
>> > I am able to get either mixed model or linear model anova and TukeyHSD,
>> > but
>> > have no luck with Repeated-Measures Assuming Sphericity or Separate
>> > Sphericity Tests.
>> > I am trying to follow example from "car" package, but it seems that I am
>> > not
>> > getting something right.
>> >
>> >> Dataset$Sessn <- as.factor(Dataset$Sessn)
>> >
>> >> LinearModel.1 <- lm(Response ~ Sessn*Trtmt, data=Dataset)
>> >
>> >> summary(LinearModel.1)
>> >
>> > All, good so far, but I have problem understanding "idata=" and
>> > "idesign="
>> > functions pertaining to my example.  Session is my repeated measure
>> > (Sessn 1
>> > and Sessn 2 = two sessions, in reality I have more) and it is already
>> > stacked. Any help or guidance on this matter.
>> >
>> > Thank you, my mock dataset is below.  Each subject has two levels of
>> > treatment throughout four calendar days which are recoded to Session 1
>> > and
>> > Session 2 in order to compare treatments by the first and subsequent
>> > days of
>> > exposure (Treatment x Session; my DV is Response; Session is repeated).
>> >
>> >    Subj Trtmt Sessn Response  1 N 1 5  1 D 1 6  1 N 2 4  1 D 2 7  2 N 1
>> > 8
>> > 2 D 1 9  2 N 2 2  2 D 2 1  3 N 1 4  3 D 1 5  3 N 2 6  3 D 2 2  4 N 1 5
>> >  4 D
>> > 1 6  4 N 2 4  4 D 2 7  5 N 1 8  5 D 1 9  5 N 2 2  5 D 2 1  6 N 1 4  6 D
>> > 1 5
>> > 6 N 2 6  6 D 2 2
>> >
>> > Sincerely,
>> >
>> > Sergios Charntikov (Sergey), MA
>> >
>> > Behavioral Neuropharmacology Lab
>> > Department of Psychology
>> > University of Nebraska-Lincoln
>> > Lincoln, NE 68588-0308  USA
>> >
>> > sergioschr-at-gmail-dot-com
>> >
>> >        [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
>> > R-help at r-project.org mailing list
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide
>> > http://www.R-project.org/posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>> >
>> >
>>
>>
>>
>> --
>> Mike Lawrence
>> Graduate Student
>> Department of Psychology
>> Dalhousie University
>>
>> Looking to arrange a meeting? Check my public calendar:
>> http://tr.im/mikes_public_calendar
>>
>> ~ Certainty is folly... I think. ~
>
>



-- 
Mike Lawrence
Graduate Student
Department of Psychology
Dalhousie University

Looking to arrange a meeting? Check my public calendar:
http://tr.im/mikes_public_calendar

~ Certainty is folly... I think. ~