Practice exercise (made-up values, not clinical guidance). A new test was compared with the reference standard in a study (see the 2 × 2 table). Find the sensitivity Se as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). A town has 6500 inhabitants. At the start of a year, 88 of them have a chronic disease. During the year, 47 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, 300 patients received a new treatment and 910 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). In a cohort, groups of people were followed for different lengths of time (see the table: number of people and years of follow-up for each). During follow-up, 9 new cases occurred. Find the incidence rate IR per 1000 person-years. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 89% and specificity 88%. The prevalence of the disease is 19%. How many false-positive results FP are expected?
Practice exercise (made-up values, not clinical guidance). A screening test has a sensitivity of 80% and a specificity of 95%. It is used in a population where the prevalence is 2%. Find the positive predictive value PPV as a percentage. Round to one decimal place.
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