randomised controlled trials and measures of impact

Question 1

basics of Randomised control trial

Answer 1

observe and change exposure, gold standard as it directly addresses counterfactuals

Question 2

counterfactuals

Answer 2

expressing what has not happened but could happen

change exposure to change risk of outcome

Question 3

RCT method

Answer 3

random group assignment, intervention and control (basics)

Question 4

control group uses

Answer 4

differences before and after could be due to another factor or not representative, minimises reverse causation

Question 5

potential issues RCT

Answer 5

loss follow up
placebo
need allocation concealment
blinding useful
statistical significance

Question 6

RCT uses

Answer 6

clinical medicine and for causal relationships

Question 7

RCT limitations

Answer 7

ethical reasons behind certain exposures

Question 8

NNT numbers needed to treat

Answer 8

average no. patients who need to be treated/intervened to prevent one additional bad outcome

Question 9

NNT formula

Answer 9

1/risk difference (round up)

greatest when risk ratio greater and when outcome is more common

Question 10

attributable fraction

Answer 10

what percentage is attributed to certain exposure

Question 11

attributable fraction formula

Answer 11

excess risk from exposure / risk

Question 12

background risk

Answer 12

even without exposure chance of developing outcome

Question 13

risk for one exposure

Answer 13

background risk times RR

Question 14

population attributable fraction

Answer 14

proportion cases in in pop. attributed to exposure