Practice exercise (made-up values, not clinical guidance). A town has 49 000 inhabitants. At the start of a year, 1170 of them have a chronic disease. During the year, 346 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, 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, 20 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, 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, 76 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 patient has a pre-test probability of 40% for a disease. A test with sensitivity 83% and specificity 66% 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 87% and a specificity of 86%. 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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