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### Logistic Regression and Unequal Distribution of Dependent Variable

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```Hello, I'm preparing to run a logit model predicting the odds of NOT
testing for an STD.

As you can see from the table below, 2934 (about 86%) of respondents have my outcome of interest (i.e., have not tested for an STD).

I realized that because of this unequal unequal distribution of the dependent variable, all crosstabulations have higher proportions within the untested category of those who have not been tested, regardless of the distribution of the other variable.

I have a feeling that these could bias my estimates in a way - since the not-tested category seemed over-estimated. For example, given the unequal groupings, I think I am only restricted to modeling failure to test (the zero outcome), as modeling for ever tested (1) could lead to unstable estimates.

So my question is it worth producing any crosstabs showing the distribution of socio-demographic variables within my outcome of interest?

What possible impact will this have on my logistic model, and what can I do about it?  Thanks - Yawo

===================>
Table 1:

RECODE of |
V827      |
(Last     |
test was  |
on your   |
own,      |
offered   |  RECODE of V501 (Current
or        |      marital status)
required) |     0      1      2  Total
----------+---------------------------
Not Test | 99.37   81.1  99.08  88.75
|   514   1563    857   2934
|
Asked fo | .2992  1.015  .2525  .6992
|     2     18      2     22
|
Offered | .2523  17.63  .1184  10.24
|     3    427      1    431
|
Test Req | .0816   .253  .5512  .3114
|     1      5      2      8
|
Total |   100    100    100    100
|   520   2013    862   3395
--------------------------------------
Key:  column percentages
number of observations
----------------------------------

Table 2:

RECODE of |
V827      |
(Last     |
test was  |
on your   |
own,      |
offered   |  RECODE of V106 (Highest
or        |     educational level)
required) |     0      1      2  Total
----------+---------------------------
Not Test | 83.34  96.84   89.9  88.75
|   724    273   1937   2934
|
Asked fo | .2094  1.662   .777  .6992
|     2      4     16     22
|
Offered | 16.37  1.497  8.887  10.24
|   209      3    219    431
|
Test Req | .0785      0  .4358  .3114
|     1      0      7      8
|
Total |   100    100    100    100
|   936    280   2179   3395
--------------------------------------
Key:  column percentages
number of observations
```
 0
Reply Yawo1964 (17) 3/8/2009 7:49:59 PM

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