SPSS® 12.0 Command Syntax Reference

808 LOGISTIC REGRESSION
Example
LOGISTIC REGRESSION PASS WITH GRE, CLASS
/CATEGORICAL = CLASS
/CONTRAST(CLASS)=HELMERT.
• A logistic regression analysis of the dependent variable PASS is performed on the interval
independent variable GRE and the categorical independent variable CLASS.
• PASS is a dichotomous variable representing course pass/fail status and CLASS identifies
whether a student is in one of three classrooms. A HELMERT contrast is requested.
Example
LOGISTIC REGRESSION PASS WITH GRE, CLASS
/CATEGORICAL = CLASS
/CONTRAST(CLASS)=SPECIAL(2 -1 -1
0 1 -1).
• In this example, the contrasts are specified with the keyword SPECIAL.
METHOD Subcommand
METHOD indicates how the independent variables enter the model. The specification is the
METHOD subcommand followed by a single method keyword. The keyword METHOD can be
omitted. Optionally, specify the independent variables and interactions for which the method
is to be used. Use the keyword BY between variable names of an interaction term.
• If no variable list is specified or if the keyword ALL is used, all of the independent variables
following the keyword WITH on the VARIABLES subcommand are eligible for inclusion
in the model.
• If no METHOD subcommand is specified, the default method is ENTER.
• Variables specified on CATEGORICAL are replaced by sets of contrast variables. The set
of contrast variables associated with a categorical variable is entered or removed from the
model as a single step.
• Any number of METHOD subcommands can appear in a Logistic Regression procedure.
METHOD subcommands are processed in the order in which they are specified. Each
method starts with the results from the previous method. If BSTEP is used, all remaining
eligible variables are entered at the first step. All variables are then eligible for entry and
removal unless they have been excluded from the METHOD variable list.
• The beginning model for the first METHOD subcommand is either the constant variable
(by default or if NOORIGIN is specified) or an empty model (if ORIGIN is specified).
The available METHOD keywords are:
ENTER Forced entry. All variables are entered in a single step. This is the default if the
METHOD subcommand is omitted.
FSTEP Forward stepwise. The variables (or interaction terms) specified on FSTEP are
tested for entry into the model one by one, based on the significance level of the
score statistic. The variable with the smallest significance less than PIN is entered
into the model. After each entry, variables that are already in the model are tested
for possible removal, based on the significance of the conditional statistic, the