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| From | Witness Chirinda <witchirinda@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: problem with predicted probabilities |
| Date | Tue, 4 Feb 2014 07:04:38 +0200 |
Thanks Nick and Richard for you help! On Sun, Feb 2, 2014 at 11:23 PM, Richard Williams <richardwilliams.ndu@gmail.com> wrote: > Getting every case classified as 0 (or 1) is not unusual. For relatively > rare events, the highest predicted probability for every case may be less > than .5, so every case gets classified as 0. My own experience is that the > classification table tends not to be that helpful, especially for events > that are very rare or very common. > > > At 04:58 AM 2/2/2014, Witness Chirinda wrote: >> >> Dear Statalist >> I want to obtain some predicted probabilities after logistic >> regression, as attached. I want to use the predicted probabilities in >> my next step instead of observed prevalence since the latter are >> adjusted for other (socio-demographic) factors. >> My problem is that the when I run - estat classification- it giving 0s >> for + classification. I am sure I am doing it the wrong way somewhere. >> Please see below output. All variables used in the model have been >> recorded to be binary 1/0 >> >> Thanks for any help! >> ------------------ >> >> >> . logistic Health_stat age maried wealth educat place sex >> >> Logistic regression Number of obs = >> 2339 >> LR chi2(6) >> = 50.61 >> Prob > chi2 >> = 0.0000 >> Log likelihood = -996.02516 Pseudo R2 = >> 0.0248 >> >> ------------------------------------------------------------------------------ >> Health_stat | Odds Ratio Std. Err. z P>|z| [95% >> Conf. Interval] >> >> -------------+---------------------------------------------------------------- >> age | 1.109083 .0342696 3.35 0.001 1.043909 1.178326 >> maried | 1.2134 .1962535 1.20 0.232 .8837556 1.666004 >> Wealth | 1.430957 .1784661 2.87 0.004 1.120641 1.827203 >> educat | 1.670411 .2010455 4.26 0.000 1.319397 2.11481 >> place | .9334522 .1223134 -0.53 0.599 .7220318 1.206779 >> sex | 1.129008 .1324642 1.03 0.301 .8970722 1.420911 >> >> . estat class >> >> Logistic model for poorSRHS >> -------- True -------- >> Classified | D ~D | Total >> -----------+--------------------------+----------- >> + | 0 0 | 0 >> - | 370 1969 | 2339 >> -----------+--------------------------+----------- >> Total | 370 1969 | 2339 >> >> Classified + if predicted Pr(D) >= .5 >> True D defined as poorSRHS != 0 >> -------------------------------------------------- >> Sensitivity Pr( +| D) 0.00% >> Specificity Pr( -|~D) 100.00% >> Positive predictive value Pr( D| +) .% >> Negative predictive value Pr(~D| -) 84.18% >> -------------------------------------------------- >> False + rate for true ~D Pr( +|~D) 0.00% >> False - rate for true D Pr( -| D) 100.00% >> False + rate for classified + Pr(~D| +) .% >> False - rate for classified - Pr( D| -) 15.82% >> -------------------------------------------------- >> Correctly classified 84.18% >> -------------------------------------------------- >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > > ------------------------------------------- > Richard Williams, Notre Dame Dept of Sociology > OFFICE: (574)631-6668, (574)631-6463 > HOME: (574)289-5227 > EMAIL: Richard.A.Williams.5@ND.Edu > WWW: http://www.nd.edu/~rwilliam > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/