User Guide

64
Chapter 6
Contrast variables are continuous. They are used to compute generalized log-odds
ratios. The values of the contrast variable are the coefficients for the linear combination
of the logs of the expected cell counts.
A cell structure variable assigns weights. For example, if some of the cells are
structural zeros, the cell structure variable has a value of either 0 or 1. Do not use a cell
structure variable to weight aggregated data. Instead, choose
Weight Cases from the
Data menu.
Assumptions. Two distributions are available in General Loglinear Analysis: Poisson
and multinomial.
Under the Poisson distribution assumption:
 The total sample size is not fixed before the study, or the analysis is not conditional
on the total sample size.
 The event of an observation being in a cell is statistically independent of the cell
counts of other cells.
Under the multinomial distribution assumption:
 The total sample size is fixed, or the analysis is conditional on the total sample size.
 The cell counts are not statistically independent.
Related procedures. Use the Crosstabs procedure to examine the crosstabulations. Use
the Logit Loglinear procedure when it is natural to regard one or more categorical
variables as the response variables and the others as the explanatory variables.