Practice exercise (made-up values, not clinical guidance). A town has 28 000 inhabitants. At the start of a year, 548 of them have a chronic disease. During the year, 159 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 50 000 inhabitants. At the start of a year, 928 of them have a chronic disease. During the year, 840 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 case-control study compares 190 patients with a disease (cases) and 120 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). In a randomised trial, 220 patients received a new treatment and 490 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). 10 000 people are screened with a test of sensitivity 89% and specificity 98%. The prevalence of the disease is 24%. How many people with the disease are missed by the test (false negatives, FN)?
Practice exercise (made-up values, not clinical guidance). A screening test has a sensitivity of 92% and a specificity of 98%. It is used in a population where the prevalence is 0.5%. Find the positive predictive value PPV as a percentage. Round to one decimal place.
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