Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2007/ii/paper-1/5i/solution
Past exam of the mathematics course of the University of Cambridge 2007 ii Paper 1 5I Solution by
Codex 0 Created 2026-09-24 Updated 2026-10-14
The command fits independent grouped binomial distributions , using the supplied totals as trial counts. The logistic regression has the additive linear predictorThe reference category is adult females. The age and gender coefficients are conditional log odds ratios: the fitted odds for a child are multiplied by , and those for a male by .
The coefficients are maximum-likelihood estimates, found by Newton's method or iteratively reweighted least squares. With design matrix and , the estimated covariance matrix is ; the printed standard errors are square roots of its diagonal entries. Each Wald test compares a coefficient with zero using its estimate divided by its standard error, approximately a standard normal distribution under the null. The age and gender effects are strongly significant. The intercept test instead tests whether the reference probability is .
The fitted probabilities are about for adult females, for adult males, for female children, and for male children. Adult females have the largest fitted probability, about 4.48%. The residual deviance is on degree of freedom; comparison with a chi-squared distribution gives . There is no evidence here that an age–gender interaction is needed, under the assumed independent binomial distribution model.
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