[R-sig-ME] aov() -> lme() conversion difficulty
Ben Bolker
bbolker at gmail.com
Wed Mar 16 16:44:00 CET 2011
On 11-03-16 10:41 AM, Brian Edward wrote:
>
> according to a couple of PDFs and webpages in came up with this aov() <- lme() conversion:
>
>
>> anova(lme(Hits~NumEyesUsed, random=~1|PersonID/NumEyesUsed,data=y))
I think you want
random = ~NumEyesUsed|PersonID
>
> numDF denDF F-value p-value
> (Intercept) 1 36 56.06667 <.0001
> NumEyesUsed 1 1 3.26667 0.3217
Your table got mangled. Was it supposed to look like this?
If so, then it's clear from the denominator DF that something is wrong ...
>
>
>> summary(aov(Hits~NumEyesUsed+Error(PersonID/NumEyesUsed),data=y))
Error: PersonID
> Df Sum Sq Mean Sq F value Pr(>F)Residuals 1 1.7514e-33 1.7514e-33
Also note that your residual errors are essentially zero, which means
you don't have any variation left after you have included experimental
blocks -- some are aliased with the residual error.
> Error: PersonID:NumEyesUsed
> Df Sum Sq Mean Sq F value Pr(>F)
> NumEyesUsed 1 4.9 4.9 12.25 0.1772
> Residuals 1 0.4 0.4
> Error: Within Df Sum Sq Mean Sq F value Pr(>F)
> Residuals 36 56.6 1.5722
>
> In this study each person is allowed try ten times with one eye and then ten times with two eyes to score hits.
> The question is if there is a difference in hits between using one or two eyes.
>
> I get different p-values in my aov() <- lme() conversion, which one answers the question more closely?
What are your actual response variables? Number of successes out of
10 tries? In that case I might suggest
lmer(cbind(Hits,10-Hits)~NumEyesUsed+(NumEyesUsed|PersonID),
family=binomial, data= ...)
although that will make it hard for you get p-values.
For that matter, since you have only two treatment levels, what's
wrong with a paired t-test ... ???
Ben Bolker
More information about the R-sig-mixed-models
mailing list