what is a case control study design?
- find people with outcome
- retrospectively look back and see if they have risk factor
what are the positives of case control studies?
- good for rare outcomes
- fast and cheap
- few ethical considerations
what are the negatives of case control studies?
- cannot prove causation/eliminate confounders
- difficult to establish order of events
- only single outcome at a time
- biases
what is a cross-sectional study design?
at this moment in time
what are the positives of a cross-sectional study?
- fast and cheap
- generates hypotheses
- little ethics
what are the negatives of a cross-sectional study?
- not causative
- less suitable for rare diseases
- difficult to establish order of events
- sample bias
what is a cohort study?
- some with and some without exposure
- no outcome
- prospectively follow up over time
what are the positives of a cohort study?
- little ethics
- clearly an event sequence
what are the negatives of a cohort study?
- cannot prove causation
- not suitable for rare/chronic diseases
- time consuming and expensive
- difficult to follow up
- people can change behaviours in cohort
what is the gold standard study design?
RCT
what is an RCT?
- multiple ‘arms’ that give different exposures
- compare outcomes
what is a cross-over RCT?
can balance arms by crossing over (giving all arms to participants)
what are the positives of an RCT?
- can directly prove causation by eliminating confounders
- less bias (random)
- can balance arms
what are the negatives of an RCT?
- time consuming and expensive
- often unethical
- issues with compliance in follow up
what are ecological studies?
- massive / all of population
- look at data, prevalence, trends, correlation
what are the positives of an ecological study?
- fast and cheap
- easy
what are the negatives of an ecological study?
- ecological fallacy (correlation does not equal causation)
