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.
Evidence-based practice statistics worksheet with answers
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, 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, 13 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 randomised trial, 710 patients received a new treatment and 660 received the control treatment. The table shows how many in each group had the outcome (an unwanted event such as a stroke). Find the relative risk RR of the event with treatment. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 92% and specificity 81%. The prevalence of the disease is 13%. How many positive results n₊ are expected in total?
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 78% and specificity 93%. The prevalence of the disease is 12%. How many true-positive results TP are expected?
Answer key
- 1. p = 21.3 %
- 2. Sp = 72 %
- 3. IR = 4 per 1000 person-years
- 4. RR = 0.79
- 5. n₊ = 2849
- 6. TP = 936
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