Purpose
Specifies the model form as multiplicative excess relative risk.
Syntax
MULTIPLICATIVE
Arguments and Subcommands
None
Remarks
The multiplicative excess relative risk model has the form
When the EXCESS or BACK commands are used to cause computation of the
estimated number of background (%BK) and excess
(%EX) following each fit, the number of background
cases is determined by the value of term 0 (T0) and
the number of excess cases is defined as the difference between the fitted and
background values (i.e. %FV - %BK). The value of
%BK is typically S T0, where
S is a scaling
factor such as the number of person years in rate regression (AMFIT) or the number of
trials in logistic regression. In this case %EX
is 
When looking at joint effects of multiple risk factors (i.e.
when n is greater than 2 or more). One is often interested in the
estimated number of excess cases associated with each exposure (Ti).
Computation of these values requires some effort, but can be done in a
relatively straightforward manner using the PARA
command with the AS option to save the parameters of
interest and some transformations. In the case of two multiplicative risk
factors the number of excess cases associated with the first of these risk
factors is 
. For the more general case of
n multiplicative risk factors the number of excess cases associated with
the ith risk factor is 
.