[R] Multivariate multiple linear regression question

[Bert Gunter]

Sorry, but please do not multiple post. That's spam.

This is a list about the R programming language, not about statistical
methods. While there is often some overlap, your questions are entirely
statistical and therefore OT here( at least imo). Try a statistical list
like stats.stackexchange.com instead.

Cheers,
Bert



On Saturday, February 20, 2016, Virendra Mishra <virendra.mishra at gmail.com>
wrote:

> Hi R-users,
>
> I have a fairly simple question to ask but I havent yet got an answer to
> the question. I will describe my experiment, analysis and what have I done
> and what is the question in the following paragraphs and I would appreciate
> if anyone could point me to use right statistical tools to answer my
> question.
>
> Experiment:
> I have 2 groups and both groups undergo 2 set of evaluations, one with MRI
> scanner and the other in the lab to test for their behavior. Both these
> evaluations are known to have statistically significant relationship with
> age and gender.
>
> Statistical question of interest:
> Whether there is:
> 1) statistically significant difference between the 2 groups on each
> evaluation ?
> 2) Whether there is any relationship between and within the 2 groups
> between each evaluation
>
> Model:
>
> I model the problem as following:
> MRI_measure = Intercept + Slope1 * Age + Slope 2 * Gender + Slope3 * Group
> [Age is continuous and gender , Group are factors/categorical]
>
> Lab_measure = Intercept + Slope1 * Age + Slope 2 * Gender + Slope3 * Group
> [Age is continuous and gender , Group are factors/categorical]
>
> In order to obtain the solution in R:
> MRI_model<-lm(cbind(MRI_measure, Lab_measure) ~ age+gender+group,
> data=data)
>
> Result of R:
> manova(MRI_model) suggests that yes indeed all the slopes are significantly
> different than 0 suggesting a relationship between my measures.
>
> Question:
> 1) In order to test whether the difference in the MRI_measure is
> statistically significant different between the 2 groups, I use
> MRI_model$fitted.values for each dependent measure and do a statistical
> test (either t-test or Wilcox) and claim that the difference is
> significant.
> In the paper I write, multivariate multiple linear regression was performed
> for the groups while controlling for age and gender. The regressed out
> MRI_measure was statistically compared to see if the difference is
> different.
>
> I am assuming that the predicted/fitted.values in model are the regressed
> out variables. Can I show this and use this result? Is this right
>
> If no, what is the correct way to statistically compare whether my 2 groups
> differ in their MRI measure and lab measure when controlled for age and
> gender. Any R library, literature, possibly a script will be greatly
> appreciated.
>
> 2) I also want to see if there is any relationship between MRI_measure and
> Lab_measure within the group after they are controlled for age and gender.
> What is the correct way to do this in R?
>
> Further, I also want to see if there is any significantly different
> association between the 2 groups for my set of dependent variables. I am
> thinking this can be done: I first find the correlation between 2 dependent
> variable in each group and test if this correlation is statistically
> different between the 2 groups? Is this logic right? And if it is, how do I
> compare the correlation? If not, what is the right way to do this? Any R
> library, literature, possibly a script will be greatly appreciated.
>
> I do appreciate any reply.
>
> Thanks
>
> Regards
>
> Virendra
>
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>
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-- 
Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

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