```Date: Mon, 24 Jan 2011 12:58:32 -0800 Reply-To: Bruce Weaver Sender: "SPSSX(r) Discussion" From: Bruce Weaver Subject: Re: problem with casewise list and classification plot in logistic regression In-Reply-To: <1295860965438-3354405.post@n5.nabble.com> Content-Type: text/plain; charset=UTF-8 You have other more serious problems to deal with here. The classification table in your output gives this frequency distribution for your outcome variable: 732 -- No Combined RMC 21 -- Combined RMC So you are severely over-fitting the model. According to the rule of thumb given in Frank Harrell's book (Regression Modeling Strategies, Springer), you should have at least 15-20 events per model parameter. An "event" is defined as the outcome variable category with the lower frequency count. So you have 21 events. Therefore, you can only really include one (single degree of freedom) explanatory variable. (Bear in mind that the constant counts as a parameter.) For more information on over-fitting, see Mike Babyak's nice readable article. http://www.class.uidaho.edu/psy586/Course%20Readings/Babyak_04.pdf HTH. lcl23 wrote: > > I am using binary logistic regression to test this model: > > logit(ρ1) = α + β1(INDDIR) + β2(INDCHAIR) + β3(BOARDSIZE) + β4(DIRSHIP) + > β5(MEETING) + β6(EXPERT) + β7(INSTI) + β8(DEBT) + β9(LnSIZE) + β10(BIG4) > > I have attached with the output of 2nd run. I have some doubt on the > casewise list (outliers). The first time I run the analysis, there were 44 > outliers. I deleted all these 44 cases. Then, I re-run the analysis. > Again, 11 outliers were appeared. I deleted all these 11 cases then > re-run. Again and again, 6 outliers were found! > > So, should I continuously delete all outliers or it would be a never > ending story? > > Also, does the classification plot looks weird? I not sure how to > interpret it. > > Please help. Thanks. > > http://spssx-discussion.1045642.n5.nabble.com/file/n3354405/OUTPUT.PDF > OUTPUT.PDF > ----- -- Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." NOTE: My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. -- View this message in context: http://spssx-discussion.1045642.n5.nabble.com/problem-with-casewise-list-and-classification-plot-in-logistic-regression-tp3354405p3355267.html Sent from the SPSSX Discussion mailing list archive at Nabble.com. ===================== 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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