Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2017/ii/paper-4/12j/a/solution

The Poisson deviance tests overall fit against the saturated Poisson regression, not whether the single slope is zero. Under fit.1, its large-count approximation is . The observed value is 261.72, far above the one-percent upper critical value (about 85.95); its upper-tail probability is about . Thus reject fit.1 at the one-percent level. The slope's reported -value 0.421 only compares this inadequate log-linear trend with an intercept-only model; it is not a goodness-of-fit test.

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