Flashcards in L5 concept of cause Deck (16):
single condition or event that invariably leads to particular outcome
what are the three conditions of cause?
1. must precede the effect
2. can involve host or environment
3. can be either positive or negative
what are the three components of cause?
1. component causes eg/ pieces of pie
2. necessary causes eg/ most important piece of pie
3. sufficient causes eg/ whole pie
component causes can occur far apart in time true or false?
describe the difference between direct and indirect cause
direct cause = no known intervening variable between exposure factor and disease
indirect cause = effect exposure meditated through one or more intervening variable
how do we determination causation, with statistics or judgment?
statistics is only used for association studies
What are the three criteria for making judgement on causation?
- koch's postulates
- hills criteria
- evans criteria
should hills criteria be used rigidly?
list the 8 factors of criteria for causation via the hills method
2. strength of association
4. plausibility and coherence
7. dose response
8. experimental evidence
some silly characters plan to annihilate dogs everywhere
describe strength of association
strong associations more likely to be causal because they are unlikely to be due entirely to bias and confounding
A WEAK ASSOCIATION DOES NOT ELIMINATE CAUSATION
has the cause and effect relationship been identified by a number of different researchers?
a single exposure should cause a single disease
- many exceptions e.g./ smoking associated w/ many diseases not just lung cancer
cause must PRECEDE the effect
- prospective studies less likely to confuse the issue of temporarlity
describe dose response relationship
level of exposure increased, rate of disease should increase
describe plausibility and coherence
causal interpretation should fit with known facts of nature, history, and biology of disease.
needs to make biological sense