Logit Model (GENLOG command)

The logit model examines the relationships between dependent and independent factor variables.

• To separate the independent variables from the dependent variables in a logit model, use the keyword BY. The categorical variables preceding BY are the dependent variables; the categorical variables following BY are the independent variables.
• Up to 10 variables can be specified, including both dependent and independent variables.
• For the logit model, you must specify MULTINOMIAL on the MODEL subcommand.
• GENLOG displays an analysis of dispersion and two measures of association—entropy and concentration. These measures are discussed elsewhere ¹ and can be used to quantify the magnitude of association among the variables. Both are proportional-reduction-in-error measures. The entropy statistic is analogous to Theil’s entropy measure, while the concentration statistic is analogous to Goodman and Kruskal’s tau-b. Both statistics measure the strength of association between the dependent variable and the independent variable set.

Example

GENLOG  GSLEVEL BY EDUC SEX 
  /MODEL=MULTINOMIAL
  /DESIGN=GSLEVEL, GSLEVEL BY EDUC, GSLEVEL BY SEX.

• The keyword BY on the variable list specifies a logit model in which GSLEVEL is the dependent variable and EDUC and SEX are the independent variables.
• A logit model is multinomial.
• DESIGN specifies a model that can test for the absence of the joint effect of SEX and EDUC on GSLEVEL.