Hi, actually I am not expert about statistic .
proc logistic model the probability of event ,not the number of event.
It is called overdispersion .
In the sas documentation of logistic has described it.
Overdispersion
For a correctly specified model, the Pearson chi-square statistic and the deviance, divided by their degrees of
freedom, should be approximately equal to one. When their values are much larger than one, the assumption
of binomial variability might not be valid and the data are said to exhibit overdispersion. Underdispersion,
which results in the ratios being less than one, occurs less often in practice.
When fitting a model, there are several problems that can cause the goodness-of-fit statistics to exceed their
degrees of freedom. Among these are such problems as outliers in the data, using the wrong link function,
omitting important terms from the model, and needing to transform some predictors. These problems should
be eliminated before proceeding to use the following methods to correct for overdispersion.
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