Practice exercise (made-up values, not clinical guidance). A town has 25 500 inhabitants. At the start of a year, 810 of them have a chronic disease. During the year, 343 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). A town has 33 000 inhabitants. At the start of a year, 1164 of them have a chronic disease. During the year, 488 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 randomised trial, 710 patients received a new treatment and 220 received the control treatment. The table shows how many in each group had the outcome (an unwanted event such as a stroke). Find the number needed to treat NNT to prevent one event. Round up to a whole number of patients.
Practice exercise (made-up values, not clinical guidance). A case-control study compares 240 patients with a disease (cases) and 600 people without it (controls). The table shows how many in each group were exposed to a risk factor. Find the odds ratio OR for the exposure. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A patient has a pre-test probability of 50% for a disease. A test with sensitivity 72% and specificity 77% comes back positive. Find the post-test probability p′ of the disease as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 92% and specificity 75%. The prevalence of the disease is 26%. How many positive results n₊ are expected in total?
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