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| From | Steve Samuels <sjsamuels@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: Intraclass Correlation for an Independent Variable? |
| Date | Thu, 12 Aug 2010 13:26:10 -0400 |
Well, I will say this: The data show that plant means in the worker measurement X differ no more than would be expected if workers had (say) been randomly assigned to plants. How the differences in plant X means arose is immaterial to whether they affect plant outcome. I think that is a response that you can give the reviewer. . To my mind, including a summary measure such as the mean of X is perfectly legitimate. Trying to find the most predictive summary X is okay, as long as you are trying to control for the possible effects of X, not test hypotheses about it. Otherwise you have to quote the p-values and coefficients for all the summaries you consider and make some statement about the multiple test problem. Steve On Thu, Aug 12, 2010 at 12:43 PM, Steve Samuels <sjsamuels@gmail.com> wrote: > Lloyd, Whether, and how, to include the worker measurements as > predictors of plant outcomes are substantive questions that I don't > think I can answer. > > Steve > > On Thu, Aug 12, 2010 at 12:22 PM, Lloyd Dumont <lloyddumont@yahoo.com> wrote: >> 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/ >>> >> >> >> >> >> >> * >> * 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/