Evidence-based practice statistics worksheet with answers

Free printable Evidence-based practice statistics worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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Name: ____________________   Date: ____________

1.Easy
testdisease presentdisease absenttotalpositive222184406abnegative148786934cdtotal3709701340

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.

a = 222b = 184c = 148d = 786
Se = %
2.Easy
testdisease presentdisease absenttotalpositive32442366abnegative76338414cdtotal400380780

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.

a = 324b = 42c = 76d = 338
Sp = %
3.Medium
eventno eventtotaltreatment81743860abcontrol365595960cd

Practice exercise (made-up values, not clinical guidance). In a randomised trial, 860 patients received a new treatment and 960 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.

treatment: 817/860control: 365/960
NNH =
4.Medium
eventno eventtotaltreatment42768810abcontrol51339390cd

Practice exercise (made-up values, not clinical guidance). In a randomised trial, 810 patients received a new treatment and 390 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.

treatment: 42/810control: 51/390
ARR = %
5.Hard
testdisease presentdisease absenttotalpositive?negativetotal10 000

Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 98% and specificity 93%. The prevalence of the disease is 29%. How many false-positive results FP are expected?

N = 10 000p = 29%Se = 98%Sp = 93%
FP =
6.Hard
p (%)PPV (%)2%PPV = ?100

Practice exercise (made-up values, not clinical guidance). A screening test has a sensitivity of 84% and a specificity of 98%. 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.

Se = 84%Sp = 98%p = 2%
PPV = %

Answer key

  1. 1. Se = 60 %
  2. 2. Sp = 88.9 %
  3. 3. NNH = 2
  4. 4. ARR = 7.9 %
  5. 5. FP = 497
  6. 6. PPV = 46.2 %

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