# Introduction to Logistic Regression

## Hands on Application: Intermediate

Now, choose two additional independent variables (try CATCH and the EMPLOYED
dummy variable) and run the multivariate
logistic regression model. Answer the following questions:
- What is the beginning -2LL?

- What is the ending -2LL?

- What are the effects of the independent variables on YES?

- Which of the independent variables are statistically significant?

- What is the interpretation of the coefficient on the dummy variable?

- Do the additional independent variables improve the overall performance of the
model? [hint: compare the model chi-square and % correct predictions statistics]

Now you are ready for even more exploration of logistic regression in SPSS:
- What is the 95% confidence interval for the odds ratio on your independent variables (in
the Logistic Regression box, click
on "options" then the "CI for e
__x__p(B)" box, then "continue")? Does the
confidence interval on the dummy variable include 1?

- Save the predicted probabilities for potential use in a later
analysis (in the Logistic Regression box, click on "save" and "probabilities" then "continue").

- Calculate the t-statistics on the coefficients for this model.

- Calculate the McFadden's-R
^{2} for this model.

- Try to "maximize your R
^{2} by including more independent variables.