Practice exercise (made-up values, not clinical guidance). A town has 30 500 inhabitants. At the start of a year, 830 of them have a chronic disease. During the year, 562 more people are newly diagnosed (assume nobody moves away or dies). Find the point prevalence P at the start of the year per 1000 inhabitants. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). A town has 44 500 inhabitants. At the start of a year, 1137 of them have a chronic disease. During the year, 466 more people are newly diagnosed (assume nobody moves away or dies). Find the cumulative incidence CI over the year per 1000 people at risk. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). In a cohort study, exposed people contributed 2500 person-years with 113 new cases, and unexposed people 1400 person-years with 25 new cases. Find the incidence rate ratio IRR (exposed versus unexposed). Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). In a randomised trial, 200 patients received a new treatment and 540 received the control treatment. The table shows how many in each group had a side effect. Find the relative risk RR of the event with treatment. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A treatment reduces the risk of an event by 23% in relative terms (RRR = 23%). In a patient group the risk without treatment (CER) is 18% over five years. Find the number needed to treat NNT for five years to prevent one event. Round up to a whole number of patients.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 81% and specificity 93%. The prevalence of the disease is 4%. How many positive results n₊ are expected in total?
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