SAN JOSÉ STATE UNIVERSITY
College of Social Work
S. W. 242
Spring 2009
Edward Cohen
Week 13 Class Notes
•
Go over test questions
•
Introduction to Logistic Regression
•
Final Paper requirements
•
Affinity group work
I.
Logistic Regression
A.
Definition and Types
1.
Binomial (or binary) logistic regression
is a form of multivariate regression which is
used
when the dependent variable is a dichotomous categorical variable
and the
independent variables are of any type
. The DV (e.g. cured/not cured; happy/not
happy; used service/didn’t use service) is coded as a dummy variable (1 = Yes, 0 =
No).
2.
Although the outcome or dependent variable is dichotomous, logistic regression is
similar to multivariate linear regression in that the purpose is to analyze the effects of
the predictor variable(s) on the dependent variable, controlling for all other IVs. In
this case, it’s
the effect of the predictor(s) on whether the outcome occurs or not
.
3.
Extensions of the logistic model include
multinomial logistic regression
, used when
there are more than two nominal categories in the DV (such as neglected, sexually
abused, or physically abused).
Ordinal logistic regression
is used when the DV is
ordinal (such as Very happy, moderately happy, moderately unhappy, and very
unhappy). In this class we will only discuss the binomial logistic regression model.
B.
The use of logistic regression started in biostatistics and epidemiology. Logistic
regression is now used in many social and hard science research fields. Its popularity
exploded after the publication of: David W. Hosmer & Stanley Lemeshow (1990).
Applied logistic regression
. New York: Wiley.
C.
Typical research questions for binomial logistic regression:
1.
“What is the likelihood of having a suicide attempt, controlling for number of
previous suicide gestures, severity of depression, ethnicity, gender?”
2.
“Does the successful completion of a substance abuse treatment program depend on
higher levels of motivation? What role do ethnicity, gender and type of drug play?”
3.
“Do support groups for released felons prevent being re-arrested, controlling for
number of previous arrests, seriousness of previous crime, and ethnicity?”
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