Summary
The episode works through four questions that students often find difficult in this lesson: whether a rate can exceed one, how prevalence can rise while incidence falls, why case fatality figures reported during an outbreak are unreliable, and what standardized rates and standardized mortality ratios allow a reader to conclude. The hosts use new worked examples, including the conversion of a cold incidence rate to a risk, a diabetes duration problem in which Sarah makes and corrects a unit error, and two towns whose SMRs cannot be ranked against each other. Real cases include global HIV trends, SARS in 2003 and the reporting of COVID-19 case fatality in March 2020. The episode closes with a discussion of disability weights in the DALY framework, on which the hosts take different positions, and four short pauses give listeners time to work a problem before the answer is given.