Strength of association

Relative risk (RR)

Likelihood that outcome will occur in one group versus the other

Odds ratio (OR)

Odds of treatment group having the outcome

Absolute risk reduction (ARR)

When risk of an undesirable outcome is less for treatment than for control group

Absolute risk increase (ARI)

When risk of an undesirable outcome is more for treatment than for control group

Number Needed to Harm (NNH)

number of people who would need to receive intervention before one additional person would be harmed (ie, have a bad outcome) EX: NNH = 100 - For every 100 people who engage in intervention/exposure X, 1 additional person would be harmed

Number Needed to Treat (NNT)

•number of people who would need to receive intervention to prevent one bad outcome or cause one additional good outcome EX: NNT = 15 - A person's chance of benefitting from this treatment is 1 in 15