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Re: st: problem with predicted probabilities
From
Witness Chirinda <[email protected]>
To
[email protected]
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
<[email protected]> 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: [email protected]
> 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:
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