Epi Info™ User Guide

Analysis Commands: LOGISTIC

Description
This command performs conditional or unconditional multivariate logistic regression with automatic dummy variables and support for multiple interactions.

Syntax
LOGISTIC <dependent variable> = <independent variable(s)> [MATCHVAR=<match variable>] [NOINTERCEPT] [OUTTABLE=<tablename>] [WEIGHTVAR=<weight variable>] [PVALUE=<PValue>]

• The <dependent variable> represents the dependent variable.
• The <independent variable(s)> represents an independent variable that can be a numeric variable, a non-numeric variable, or a variable surrounded by parenthesis. Any text or yes-no variable, or a variable surrounded with parenthesis, is automatically recoded into dummy variables. A dummy variable is created for all but one of the levels of a variable. The variable measures the contribution of its level relative to the excluded level. Interactions are specified by * between variables.
• The <weight variable> represents a variable to specify the contribution each data row has to the output.
• The <match variable> represents a variable to specify the different groups for a conditional analysis. If a match variable is specified, a conditional analysis will be performed
• The <tablename> represents a table where the residuals are stored. If no table name is present, no residuals are produced.
• The <PValue> represents the size of the confidence intervals; this may be specified as percent or decimal. If greater than .5, 1-PValue is used. The default is 95%.

Comments
LOGISTIC uses the Newton-Rhapson method for maximizing likelihood.

Example
To do an unconditional regression, run the following:

READ  {.\Projects\Sample\Sample.prj}:Oswego 
LOGISTIC Ill = BrownBread CabbageSal Water Milk Chocolate Vanilla