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Re: st: Intraclass Correlation for an Independent Variable?


From   Lloyd Dumont <lloyddumont@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Intraclass Correlation for an Independent Variable?
Date   Thu, 12 Aug 2010 09:22:01 -0700 (PDT)

Thank you for your advice on this, Steve.  From a technical/statistical point-of-view, it was very helpful.  I ran -loneway- on the dataset of individual workers.  The F-stat was about 1.24, generating a p-value far greater than I would have wanted in order to please the reviewer--about .24.

Given that, is there anything I can do to make the case for these measures?  Is there a way to "correct for" the heterskedasticity of the estimated means for each plant before collapsing them into a dataset of plant-months?  Off the top of my head, the first thing I thought of was to -collapse- the data using medians as opposed to means.  That way, I could at least be assured that outliars are not influencing each plant's score.  Interestingly, when I did that, the results in the regression of plant-months became a little stronger.

Thank you again.  Lloyd

--- On Wed, 8/11/10, Steve Samuels <sjsamuels@gmail.com> wrote:

> From: Steve Samuels <sjsamuels@gmail.com>
> Subject: Re: st: Intraclass Correlation for an Independent Variable?
> To: statalist@hsphsun2.harvard.edu
> Date: Wednesday, August 11, 2010, 5:47 PM
> I didn't read the second part of your
> message closely enough.  ICCs
> can be computed for any variable measured in groups,and the
> reviewer's
> terminology is impeccable.  -loneway- should do what
> you want. But
> "search intraclass, all" will find some extensions.
> 
> Steve
> 
> On Wed, Aug 11, 2010 at 5:05 PM, Steve Samuels <sjsamuels@gmail.com>
> wrote:
> > The reviewer could well want to know if the plant
> differences in the X
> > means are real.  So, yes, he or she could really mean
> "X".  This is
> > the kind of question you'd test with a one-way ANOVA,
> or KW. You will
> > need the data from the individual worker X
> measurements, or the
> > plant-specific sample sizes and  variances.
> >
> > Steve
> > On Wed, Aug 11, 2010 at 4:36 PM, Lloyd Dumont <lloyddumont@yahoo.com>
> wrote:
> >> Hello.  I have gotten a confusing note from a
> reviewer, confusing in part because I think he/she is using
> the wrong terminology.
> >>
> >>
> >> In a nutshell…
> >>
> >> I am running a cross-sectional time series model
> (on a dataset of plant-months) of a continuous variable Y
> measured at the plant level where the focal, continuous
> independent variable is X.  X is also at the plant-level,
> but is time-constant.  X is formed by taking the mean level
> of X from all of the individual workers in each plant.
> >>
> >> The reviewer suggests that I include some measure
> of within versus between plant variance in X.  This would
> bolster the case that there is a genuine difference across
> plants rather than average differences simply reflecting
> noise.  He/she then goes on to suggest I do this by
> reporting intraclass correlations (ICCs).
> >>
> >> As far as I understand it, ICCs (or rho) describe
> the variance in Y, not X.  If I am right, then the reviewer
> did not mean ICC.
> >>
> >> Rather, he/she wants me to go back to the dataset
> of individuals (not plant-months) and wants me to run some
> simple analysis to show that there is clustering of values
> for X by plant.
> >>
> >> Am I correctly understanding what the reviewer is
> asking for?  And, if so, what is the simplest way to
> demonstrate the sort of dependence he/she is hoping to see?
> >>
> >> Thank you for your help.  Lloyd
> >>
> >>
> >>
> >>
> >>
> >>
> >> *
> >> *   For searches and help try:
> >> *   http://www.stata.com/help.cgi?search
> >> *   http://www.stata.com/support/statalist/faq
> >> *   http://www.ats.ucla.edu/stat/stata/
> >>
> >
> >
> >
> > --
> > Steven Samuels
> > sjsamuels@gmail.com
> > 18 Cantine's Island
> > Saugerties NY 12477
> > USA
> > Voice: 845-246-0774
> > Fax:    206-202-4783
> >
> 
> 
> 
> -- 
> Steven Samuels
> sjsamuels@gmail.com
> 18 Cantine's Island
> Saugerties NY 12477
> USA
> Voice: 845-246-0774
> Fax:    206-202-4783
> 
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
> 


      


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