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Epidemological studies - Coggle Diagram

- - - - measure frequencies (health and exposure) at a particular point in time
    - - compare disease frequencies in exposed and non-exposed induviduals
    - - compare exposures of those with and without disease
    - - there is no attempt to influence outcome
      - measures the exposure and calculate the outcome relationship
      - unable to manipulate exposure
      - cohort allocation is not random
  - - - only type of trial that can give a definite causal inference
      - experimental group = intervention
      - control group = conventional treatment/placebo
      - both groups followed to assess intervention in comparison to placebo
      - gold standard! for relationship between cause and effect
      - only difference between both groups should be treatment
      - WHY NOT??
        
        unethical - exposure can be manipulated/allocation is random
        
        not feasible due to length of study needed
        
        cannot evaluate rare outcomes - populations to small to randomise
- - - - disease frequencies in relation to population exposure