Date:         Thu, 24 Jan 2008 09:54:14 -0700
Reply-To:     Marc Mackert <Marc.Mackert@state.co.us>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Marc Mackert <Marc.Mackert@state.co.us>
Subject:      Logistic Regression Interpretation Questions
Content-Type: text/plain; charset=UTF-8

I am working on a study that involves a one-group posttest only design.
I am using logistic regression to test a Dichotomous Dependent Variable.
 I have several Independent Variables. Specifically the study includes
seven independent variables. These IVS are all ratio, scaled from 0-1. 
The analysis also includes control/intervening variables that are a
mixture of scale and categorical variables. Specifically, 1 scale and 12
categorical variables.  
 
I have entered my variables into the logistic regression model in 4
blocks. This is my first experience using logistic regression  and I am
confused by some of the results I am getting and the correct way to
interpret the results. I have several questions:
 
The first question is how high is too high for a -2LL. My -2LL is near
3000. 
 
The next question is related to the interpretation of the tests of
model fit. The Omnibus Tests of  Model Coefficients are all significant
at the <p.000 level for each block. However,  the Hosmer Lemeshow test
shows model fit for blocks 1 and 4 – not for Block 2 or 3. I am confused
as to whether I should analyze the regression models 1 and 4? I will say
  my hypotheses testing is more concerned with blocks 3 and 4 than with
blocks 1 and 2. 
 
Simply put, when analyzing logistic regression where variables have
been entered in as blocks, if the data do not fit the model in early
blocks – is it correct that the analyses stops there?
 
I am looking for both a reference if anyone can suggest one or
technical expertise/advice if it is available.
 
 
 
 
Marc J. Mackert, Ph.D.
Manager
Administrative Review Division
4045 S. Lowell Blvd.
Denver, Colorado 80236
Office: (303) 866-7137
Cell: (303) 947-3106
www.cdhs.state.co.us/ard 

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