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
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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
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
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.
Administrative Review Division
4045 S. Lowell Blvd.
Denver, Colorado 80236
Office: (303) 866-7137
Cell: (303) 947-3106
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