Evidence based practice 3a - Introduction to RCT


1. You wish to look for evidence for the effectiveness of a new treatment over conventional treatment. Which TWO of the following sources of evidence are the most valid?

Choose 2 of the following options.
   Case-control study
   Qualitative study
   Systematic review of randomised controlled trial
   Expert opinion
   Randomised controlled trial
   Cohort study


2. Which of the following statements about the control group in a randomised controlled trial are correct?

Choose 3 of the following options.
   Subjects may receive placebo treatment.
   Subjects may receive the experimental treatment.
   Subjects may receive conventional treatment.
   Subjects in the control group can be assumed not to have achieved the measured outcome.
   Subjects in the control group should be given less attention by the researcher than subjects in the experimental group.
   Outcome should be assessed in the same way as subjects in the experimental group.


3. Which of the following statements about placebo control are true?

Choose 2 of the following options.
   Subjects given a placebo usually have a worse outcome than subjects given nothing.
   The experimental subjects should be given a placebo.
   The subjects should not know that they are receiving placebo.
   The placebo should appear (e.g. look, taste, feel) the same as the experimental treatment.


4. The purpose of randomisation in a randomised controlled trial is to ensure that

One answer only.
   subjects in the experimental and control groups are similar at the end of the trial
   subjects in the experimental and control groups are similar at the start of the trial
   measurement of the outcome is unbiased
   a large proportion of subjects agree to participate in the trial


5. Which of the following statements on blinding are correct?

Choose 2 of the following options.
   The subjects know what treatments they receive in a double blind trial
   The subjects know what treatments they receive in a single blind trial
   The health professionals know what treatments the subjects receive in a single blind trial
   It helps to reduce the placebo effect.


6. In a randomised controlled trial on the use of antibiotics for sore throat, 200 subjects were allocated to the control (placebo) group and 100 subjects were allocated to the experimental group (augmentin). However, it was found after the trial that 30 subjects in the control group actually took augmentin, and 20 subjects in the experimental group actually did not take any treatment. In an intention-to-treat analysis, the number of subjects analysed in the control group is

One answer only.
   80
   100
   170
   180
   200


7. Following on from question 6, in an intention-to-treat analysis, the number of subjects to be analysed in the experimental group is

One answer only.
   80
   100
   170
   180
   200


8. Questions 8 to 13 are related to the following scenario. In a randomised controlled trial on the effectiveness of drug X to reduce mortality, there were 200 and 100 subjects in the control and experimental groups respectively. At the end of the trial, 120 and 40 subjects died in the control and experimental groups respectively. Taking death as an event, the experimental event rate (EER) is

One answer only.
   20%
   30%
   40%
   50%
   60%
   70%
   80%


9. The control event rate (CER) is

One answer only.
   20%
   30%
   40%
   50%
   60%
   70%
   80%


10. The relative risk of dying (experimental vs control) is

One answer only.
   0.5
   0.67
   1
   1.5
   2
   4


11. The absolute risk reduction (ARR) is

One answer only.
   0.2 (20%)
   0.4 (40%)
   0.5 (50%)
   0.6 (60%)
   0.8 (80%)


12. The numbers needed to treat (NNT) to reduce one extra death is

One answer only.
   2
   4
   5
   6
   8
   10
   12


13. The relative risk reduction (RRR) is

One answer only.
   0.2
   0.33
   0.4
   0.5
   0.67
   0.8