Practice exercise (made-up values, not clinical guidance). A town has 3000 inhabitants. At the start of a year, 85 of them have a chronic disease. During the year, 28 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 sensitivity Se as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). In a cohort study, exposed people contributed 1200 person-years with 54 new cases, and unexposed people 3700 person-years with 111 new cases. Find the incidence rate ratio IRR (exposed versus unexposed). Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A test has a sensitivity of 73% and a specificity of 97%. Find the positive likelihood ratio LR+. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A patient has a pre-test probability of 30% for a disease. A test with sensitivity 85% and specificity 93% 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). A screening test has a sensitivity of 88% and a specificity of 96%. It is used in a population where the prevalence is 2%. Find the negative predictive value NPV as a percentage. Round to one decimal place.
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