FRCS Statistics, Ethics & Law

Question 1

A new diagnostic test for bowel cancer has a sensitivity of 85% and a specificity of 90%. What does the specificity of 90% tell you?

Accepted Answer

90% of patients without bowel cancer will test negative

Answer

85% of patients with bowel cancer will test positive

Answer

10% of patients with bowel cancer will be missed

Answer

85% of patients without bowel cancer will test negative

Question 2

What is the number needed to treat (NNT) if a treatment reduces the absolute risk of complication from 20% to 15%?

Accepted Answer

20

Answer

5

Answer

10

Answer

15

Question 3

In a randomised controlled trial, what is the purpose of blinding participants and investigators?

Accepted Answer

To reduce performance bias and detection bias by preventing knowledge of treatment allocation

Answer

To reduce the sample size required

Answer

To prevent selection bias at randomisation

Answer

To ensure equal numbers in each group

Question 4

What is the difference between relative risk reduction (RRR) and absolute risk reduction (ARR)?

Accepted Answer

ARR is the percentage reduction in event rate between treatment and control groups; RRR is ARR divided by control event rate

Answer

They are the same measure expressed differently

Answer

RRR is always smaller than ARR

Answer

ARR is only used for negative outcomes; RRR for positive outcomes

Question 5

What type of study design provides the highest level of evidence in a hierarchy of evidence?

Accepted Answer

Systematic review and meta-analysis of RCTs

Answer

Case report

Answer

Cohort study

Answer

Randomised controlled trial

Question 6

In a clinical trial, a p-value of 0.03 is reported. What does this mean?

Accepted Answer

If the null hypothesis were true, there is a 3% probability of observing results at least as extreme as those found

Answer

There is a 3% chance the treatment is effective

Answer

There is a 97% chance the null hypothesis is true

Answer

The result is clinically significant with 97% certainty