Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/iii/paper-218/1/d/solution

The Quasi-Poisson standard errors are trustworthy only if observations are independent, the log-linear mean is correct, and the variance is proportional to the mean with one common dispersion. Dependence, zero inflation, or covariate-dependent dispersion can invalidate this covariance formula.
A parametric bootstrap under model 1 proceeds as follows. Fit the Poisson model once and retain and the fitted means . For bootstrap repetition , independently draw
refit the same Poisson regression to , and save its gender estimate . The sample standard deviation of these estimates over many repetitions estimates the model-1 standard error. This bootstrap deliberately measures uncertainty under the fitted Poisson model; it does not repair real overdispersion unless the resampling model is enlarged to represent its cause.

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