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 absenttotalpositive249104353abnegative41506547cdtotal290610900

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.

a = 249b = 104c = 41d = 506
NPV = %
2.Easy
testdisease presentdisease absenttotalpositive234103337abnegative26587613cdtotal260690950

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 = 234b = 103c = 26d = 587
Se = %
3.Medium
testdisease presentdisease absenttotalpositive285175460abnegative8515751660cdtotal37017502120

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 likelihood ratio LR+. Round to two decimal places.

a = 285b = 175c = 85d = 1575
LR+ =
4.Medium
eventno eventtotaltreatment113147260abcontrol142348490cd

Practice exercise (made-up values, not clinical guidance). In a randomised trial, 260 patients received a new treatment and 490 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: 113/260control: 142/490
NNH =
5.Hard
pre-test40%post-test?p′LR+

Practice exercise (made-up values, not clinical guidance). A patient has a pre-test probability of 40% for a disease. A test with sensitivity 69% and specificity 61% comes back positive. Find the post-test probability p′ of the disease as a percentage. Round to one decimal place.

pre-test 40%Se = 69%Sp = 61%positive
p′ = %
6.Hard
testdisease presentdisease absenttotalpositive?negativetotal10 000

Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 72% and specificity 92%. The prevalence of the disease is 9%. How many false-positive results FP are expected?

N = 10 000p = 9%Se = 72%Sp = 92%
FP =

Answer key

  1. 1. NPV = 92.5 %
  2. 2. Se = 90 %
  3. 3. LR+ = 7.7
  4. 4. NNH = 7
  5. 5. p′ = 54.1 %
  6. 6. FP = 728

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