spint.dispersion.phi_disp

spint.dispersion.phi_disp(model)

Test the hypothesis that var[y] = mu (equidispersion) against the alternative hypothesis (quasi-Poisson) that var[y] = phi * mu where mu is the expected value of y and phi is an estimated overdispersion coefficient which is equivalent to 1+alpha in the alternative alpha dispersion test.

phi > 0: overdispersion phi = 1: equidispersion phi < 0: underdispersion

Parameters

modelModel results class

function can only be called on a sucessfully fitted model which has a valid response variable, y, and a valid predicted response variable, yhat.

alt_varfunction

specifies an alternative varaince as a function of mu. Function must take a single scalar as input and return a single scalar as output

Returns

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array[alpha coefficient, tvalue of alpha, pvalue of alpha]