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 prevalence in the study p as a percentage. 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 specificity Sp as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). In a cohort study, exposed people contributed 6800 person-years with 102 new cases, and unexposed people 4600 person-years with 138 new cases. Find the incidence rate ratio IRR (exposed versus unexposed). Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). In a randomised trial, 340 patients received a new treatment and 900 received the control treatment. The table shows how many in each group had the outcome (an unwanted event such as a stroke). Find the absolute risk reduction ARR as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 77% and specificity 83%. The prevalence of the disease is 9%. How many people with the disease are missed by the test (false negatives, FN)?
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 98% and specificity 75%. The prevalence of the disease is 22%. How many positive results n₊ are expected in total?
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