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 negative predictive value NPV as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). In a randomised trial, 610 patients received a new treatment and 600 received the control treatment. The table shows how many in each group had a side effect. Find the number needed to harm NNH: how many patients must be treated for one extra patient to have the side effect? Round up to a whole number of patients.
Practice exercise (made-up values, not clinical guidance). In a cohort study, exposed people contributed 4300 person-years with 447 new cases, and unexposed people 3800 person-years with 99 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 94% and specificity 77%. The prevalence of the disease is 4%. How many true-positive results TP are expected?
Practice exercise (made-up values, not clinical guidance). A patient has a pre-test probability of 25% for a disease. A test with sensitivity 60% and specificity 87% comes back positive. Find the post-test probability p′ of the disease as a percentage. Round to one decimal place.
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