Copyright © 1990-2008 StatsDirect Limited, all rights reserved
Download a free trial of StatsDirect
Lots of things can be associated with outcomes that we wish to study but few of them are meaningful causes.
In Epidemiology, the following criteria due to Bradford-Hill are used as evidence to support a causal association:
Plausibility (reasonable pathway to link outcome to exposure)
Consistency (same results if repeat in different time, place person)
Temporality (exposure precedes outcome)
Strength (with or without a dose response relationship)
Specificity (causal factor relates only to the outcome in question - not often)
Change in risk factor (i.e. incidence drops if risk factor removed)
Elwood's criteria are a modern extension of this concept:
Descriptive evidence
exposure or intervention
design
population
main result
Non-causal explanation
chance
bias
confounding
Positive features
time
strength
dose-response
consistency
specificity
Generalisability
to eligible population
to source population
to other populations
Comparison with other
evidence
consistency
specificity
plausibility and coherence