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 specificity Sp as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). A town has 48 500 inhabitants. At the start of a year, 1855 of them have a chronic disease. During the year, 604 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 new test was compared with the reference standard in a study (see the 2 × 2 table). Find the negative likelihood ratio LR−. Round to two decimal places.
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, 8 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). A treatment reduces the risk of an event by 12% in relative terms (RRR = 12%). In a patient group the risk without treatment (CER) is 31% 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 82% and specificity 85%. The prevalence of the disease is 16%. How many true-positive results TP are expected?
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