n' = exp(persons*b1 + livebait*b2 + b3)
Note: it is possible that visitors who attempt to catch fish may fail,
thus also generating a zero count.
It is the third equation (/lncount) that models the degree of overdispersion
and divides the zero counts between those not attempting to fish and those
attempting to fish but failing to catch fish. (However, the coefficient does
not enter directly into manually estimating the counts.)
The final step is to modify the count, n', to account for attempts to catch
fish, giving the overall modeled count as:
n = n' * [1 - P(n=0)]
This count matches that generated by -predict-.
Tom
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