measures of association Flashcards
what are measures of strength
- risk ratio
- odds ratio
what are measures of impact
- risk difference
- attributable fraction
- number needed to treat
outcomes
disease, cure
exposures
risk factors
interventions
treatments
vet research compares association between
outcomes and exposure or intervention
odds
- ratio of one outcome to that of an alternative outcome
- calculated as number of outcomes divided by number on non outcomes
- 51 boys in 100 births, ODDS any birth is a boy is 51/49=1.04
risk
- probability an outcome will happen
- calculated as number of outcomes divided by total number
- 51 boys in 100 births; RISK of having a boy is 51/100=0.51
risk to odds
odds= risk/ (1-risk)
odds to risk
risk= odds/ (odds+ 1)
risk of disease in exposed and risk of disease in non exposed
just like normal thinking
either a/(a+b) or c/(c+d)
odds of disease in exposed or non-exposed
either a/b
or c/d
risk ratio
a/ (a+b) OVER c/(c+d)
Risk of exposed / risk of non exposed
ratio of the risk of disease in the exposed group to risk of disease in the unexposed group
odds ratio
a/b OVER c/d
which = ad/bc
the ratio between the odds of disease of exposed to odds of disease in unexposed group
RR interpretation
RR=1 then no exposure between exposure/ treatment and disease/cure
RR < 1 then exposure/ treatment reduces risk of disease/cure
RR>1 exposure/ treatment increases risk of disease/cure