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 accuracy Acc 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 positive predictive value PPV as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). In a randomised trial, 180 patients received a new treatment and 670 received the control treatment. The table shows how many in each group had the outcome (an unwanted event such as a stroke). Find the number needed to treat NNT to prevent one event. Round up to a whole number of patients.
Practice exercise (made-up values, not clinical guidance). A case-control study compares 200 patients with a disease (cases) and 470 people without it (controls). The table shows how many in each group were exposed to a risk factor. Find the odds ratio OR for the exposure. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A patient has a pre-test probability of 5% for a disease. A test with sensitivity 64% and specificity 79% 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). 10 000 people are screened with a test of sensitivity 71% and specificity 85%. The prevalence of the disease is 15%. How many people with the disease are missed by the test (false negatives, FN)?
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