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Date:         Tue, 9 Sep 2008 14:03:21 -0700
Reply-To:     SR Millis <srmillis@yahoo.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         SR Millis <srmillis@yahoo.com>
Subject:      Re: Fw: Re: Logistic Regression - Threshold effect sizes?
Comments: To: Jon Bernard <jon563@gmail.com>
In-Reply-To:  <cd3517fa0809091257h4ce572b2i10d923856b691edf@mail.gmail.com>
Content-Type: text/plain; charset=us-ascii

Jon,

Could you provide all of the SPSS output? SPSS is not my "main" statistical software so I am less familiar with its conventions.

Thanks, Scott Millis

--- On Tue, 9/9/08, Jon Bernard <jon563@gmail.com> wrote:

> From: Jon Bernard <jon563@gmail.com> > Subject: Re: Fw: Re: Logistic Regression - Threshold effect sizes? > To: SPSSX-L@LISTSERV.UGA.EDU > Date: Tuesday, September 9, 2008, 3:57 PM > Thanks again Scott. > > I tried this method and now have to make sense of the > output. I entered one > ordinal covariate and one binary DV, selecting the option > for contrasts as > you explained below. > > The results give the following Exp(B)'s (all of them > significant at p < > .001): > var1(1) = 2.704 > var1(2) = 2.198 > var1(3) = 1.649 > var1(4) = 1.189 > > Could I interpret this as suggesting that the impact of a > one-point positive > change in response to the item is greater when the baseline > value is 1 than > when it is 2, 3, or 4? > > Thank you, > > Jon > > > > On Fri, Sep 5, 2008 at 6:36 PM, SR Millis > <srmillis@yahoo.com> wrote: > > > Jon, > > > > If you're using SPSS binary logistic regression, > enter your ordinal > > variable as a covariate. Then, click on the > Categorical button. This will > > take you to a new window where you indicate which > covariates are > > categorical. The Contrast should be > "Indicator." Then run the analysis. > > > > If you're using Stata software, you use the xi > option. > > > > Scott Millis > > > > > > > > > > --- On Fri, 9/5/08, Jon Bernard > <jon563@gmail.com> wrote: > > > > > From: Jon Bernard <jon563@gmail.com> > > > Subject: Re: Fw: Re: Logistic Regression - > Threshold effect sizes? > > > To: "SR Millis" > <srmillis@yahoo.com> > > > Cc: SPSSX-L@listserv.uga.edu > > > Date: Friday, September 5, 2008, 6:24 PM > > > Thank you Scott. Would you recommend any > resources for a > > > quick study on > > > this technique? > > > > > > Jon > > > > > > On Fri, Sep 5, 2008 at 6:18 PM, SR Millis > > > <srmillis@yahoo.com> wrote: > > > > > > > Jon, > > > > > > > > If you're uncomfortable treating your > ordinal > > > variable > > > > as though it were interval, you can always > "dummy > > > > code" the ordinal variable---such that > the > > > 5-category > > > > variable become 4 separate variables---and > direct > > > > comparisons can be made. This can work > pretty well if > > > you > > > > don't have a lot of ordinal vairables > and if > > > you're > > > > sample size is sufficiently large. > > > > > > > > Scott Millis > > > > > > > > > --- On Fri, 9/5/08, Justin Black > > > > > <justin.black@gmail.com> wrote: > > > > > > > > > > > From: Justin Black > > > <justin.black@gmail.com> > > > > > > Subject: Re: Logistic Regression - > Threshold > > > effect > > > > > sizes? > > > > > > To: "SR Millis" > > > <srmillis@yahoo.com> > > > > > > Date: Friday, September 5, 2008, > 6:13 PM > > > > > > Scott, thank you for following up. > > > > > > > > > > > > What's puzzling to me is the > seemingly > > > omnibus > > > > > nature > > > > > > of the effect. So, I > > > > > > could say that a 1-point increase > in IV1 is > > > associated > > > > > with > > > > > > a, e.g., 40% > > > > > > increase in the likelihood of the > event > > > occurring. > > > > > But > > > > > > that assumes that a > > > > > > 1-point increase in the IV has the > same > > > effect on the > > > > > DV > > > > > > regardless of the > > > > > > baseline level of the IV. I > don't think > > > that > > > > > > assumption is accurate in > > > > > > these particular data. > > > > > > > > > > > > I really feel like I'm missing > something > > > here, > > > > > just > > > > > > can't figure out what. > > > > > > A look back at Hosmer & > Lemeshow > > > didn't help > > > > > any. > > > > > > > > > > > > Thank you, > > > > > > > > > > > > Jon > > > > > > > > > > > > On Fri, Sep 5, 2008 at 6:00 PM, SR > Millis > > > > > > <srmillis@yahoo.com> wrote: > > > > > > > > > > > > > Jon, > > > > > > > > > > > > > > What is puzzling in the > results? > > > > > > > > > > > > > > Have you examined the degree > of > > > collinearity > > > > > among the > > > > > > > predictors/covariates? > > > > > > > > > > > > > > > > > > > > > > > > > > > > Scott R Millis, PhD, MEd, > ABPP > > > (CN,CL,RP), CStat > > > > > > > Professor & Director of > Research > > > > > > > Dept of Physical Medicine > & > > > Rehabilitation > > > > > > > Wayne State University School > of > > > Medicine > > > > > > > 261 Mack Blvd > > > > > > > Detroit, MI 48201 > > > > > > > Email: smillis@med.wayne.edu > > > > > > > Tel: 313-993-8085 > > > > > > > Fax: 313-966-7682 > > > > > > > > > > > > > > > > > > > > > --- On Fri, 9/5/08, Jon > Bernard > > > > > > <jon563@gmail.com> wrote: > > > > > > > > > > > > > > > From: Jon Bernard > > > <jon563@gmail.com> > > > > > > > > Subject: Logistic > Regression - > > > Threshold > > > > > effect > > > > > > sizes? > > > > > > > > To: > SPSSX-L@LISTSERV.UGA.EDU > > > > > > > > Date: Friday, September > 5, 2008, > > > 5:42 PM > > > > > > > > Fellow SPSSers, > > > > > > > > > > > > > > > > I am struggling with a > logistic > > > regression > > > > > issue > > > > > > and > > > > > > > > thought I'd put it > out > > > > > > > > to the list for some > clarity. > > > > > > > > > > > > > > > > The dependent variable > of interest > > > is a > > > > > binary > > > > > > event (0 = > > > > > > > > Did not happen, 1 > > > > > > > > = Did happen). The > independent > > > variables of > > > > > > interest are > > > > > > > > ordinal > > > > > > > > attitudinal survey > items, with > > > responses on > > > > > a > > > > > > 5-point scale > > > > > > > > (1 = Strongly > > > > > > > > Disagree, 5 = Strongly > Agree). I > > > have been > > > > > using > > > > > > logistic > > > > > > > > regression for > > > > > > > > the analysis, but either > I'm > > > missing > > > > > > something in the > > > > > > > > results output or > I'm > > > > > > > > using the wrong > statistical > > > technique. I > > > > > have an > > > > > > inkling > > > > > > > > that the intervals > > > > > > > > between categories of > the > > > independent > > > > > variables > > > > > > are not all > > > > > > > > equal. In other > > > > > > > > words, I think that the > impact on > > > the > > > > > dependent > > > > > > variable of > > > > > > > > an independent > > > > > > > > variable score of 3 vs. > one of 2 > > > is greater > > > > > than > > > > > > that of a > > > > > > > > score of 5 vs. > > > > > > > > one of 4. Is that > clear? If so, > > > what would > > > > > you > > > > > > recommend > > > > > > > > in order to test > > > > > > > > that hypothesis? Is > there a class > > > of > > > > > techniques > > > > > > designed > > > > > > > > particularly for > > > > > > > > this kind of test? > > > > > > > > > > > > > > > > Very many thanks in > advance for > > > your > > > > > assistance > > > > > > with this > > > > > > > > matter. > > > > > > > > > > > > > > > > Kind regards, > > > > > > > > > > > > > > > > Jon > > > > > > > > > > > > > > > > ===================== > > > > > > > > To manage your > subscription to > > > SPSSX-L, send > > > > > a > > > > > > message to > > > > > > > > > LISTSERV@LISTSERV.UGA.EDU (not to > > > SPSSX-L), > > > > > with > > > > > > no body > > > > > > > > text except the > > > > > > > > command. To leave the > list, send > > > the command > > > > > > > > SIGNOFF SPSSX-L > > > > > > > > For a list of commands > to manage > > > > > subscriptions, > > > > > > send the > > > > > > > > command > > > > > > > > INFO REFCARD > > > > > > > > > > > > > > > ===================== > > > > To manage your subscription to SPSSX-L, send > a message > > > to > > > > LISTSERV@LISTSERV.UGA.EDU (not to SPSSX-L), > with no > > > body text except the > > > > command. To leave the list, send the command > > > > SIGNOFF SPSSX-L > > > > For a list of commands to manage > subscriptions, send > > > the command > > > > INFO REFCARD > > > > > > > > ===================== > To manage your subscription to SPSSX-L, send a message to > LISTSERV@LISTSERV.UGA.EDU (not to SPSSX-L), with no body > text except the > command. To leave the list, send the command > SIGNOFF SPSSX-L > For a list of commands to manage subscriptions, send the > command > INFO REFCARD

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