Statistics

Question 1

Define numbers needed to treat

Answer 1

The number of patients you need to treat to prevent one additional bad outcome (or an additional beneficial outcome).

The number of people with a specified condition, who need to be treated for a specified period of time in order to prevent one beneficial outcome (NNT to benefit) or adverse outcome (NTT harm).

Question 2

Risk ratio or relative risk

Answer 2

Risk of developing disease associated with an exposure divide by risk of developing disease in absence of disease or an exposure

RR = risk in exposed / risk of non-exposed

RR = 1 no difference between groups
RR > 1 increased risk
RR < 1 reduced risk

x fold risk