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 44 000 inhabitants. At the start of a year, 1619 of them have a chronic disease. During the year, 278 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). 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, 16 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). In a cohort study, exposed people contributed 7300 person-years with 584 new cases, and unexposed people 7700 person-years with 154 new cases. Find the incidence rate ratio IRR (exposed versus unexposed). Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 87% and specificity 91%. The prevalence of the disease is 19%. How many positive results n₊ are expected in total?
Practice exercise (made-up values, not clinical guidance). A screening test has a sensitivity of 73% and a specificity of 99%. It is used in a population where the prevalence is 5%. Find the negative predictive value NPV as a percentage. Round to one decimal place.
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