SAN JOSÉ STATE UNIVERSITY College of Social WorkS. W. 242Spring 2009Edward CohenWeek 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 regressionis a form of multivariate regression which is used when the dependent variable is a dichotomous categorical variableand 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?” 1
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