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Worked exercises

Practice problems for medical biostatistics, each with a full step-by-step solution. The method is always the same: build a cohort, split it, read the answer off the table — the technique that survives exam pressure.

Predictive values: 10 worked exercises

2×2 tables · Bayes · likelihood ratios · the case–control trap

Ten problems on PPV and NPV, from a first 2×2 table to the traps that catch clinicians: reading a table backwards, the same test in two clinics, working back to a prevalence, the NPV illusion, and why screening runs in two stages. Each states the problem, then folds the full solution away.