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ANALYTICAL STUDIES :chart: (EXPERIMENTAL (STUDIES (investigators control…
ANALYTICAL STUDIES :chart:
EXPERIMENTAL
PURPOSE
answer specific question
STUDIES
random assignment
investigators control
subjects exposed
objects exposed
prospective
best design to establish causal relationship
OBSERVATIONAL (NON-EXPERIMENTAL)
CHARACTERISTIC
establish association
not necessarily causal
IF not carefully desgined
bias
issue
describe sample or population
TYPES OF STUDIES
cross-sectional
snapshot in time
no comparison group in the initial design
only show association
the WEAKEST
cohort
Follow-up study
investigator no control exposure
similar to experimental design
randomization
exposed / treatment
unexposed / placebo
cohort - not randomizing
how work
exposed
outcome/ no disease
outcome/ disease
unexposed
outcome/disease
outcome/ no disease
there's a follow up time
follow-up time
prospective
retrospective
establish association, but not causal relationship unless have following
temporal sequencing
biological plausibility
characteristic
2 groups
samples don't have disease,
differ according to exposure
defined by exposure
good for RARE EXPOSURE
multiple outcome
one exposure
case control
opposite from cohort
disease
non-disease
retrospective: look back ascertain exposure
establish relationship, not cause
proceeds from effect to cause
STUDY RARE OUTCOMES
pre-post A-B
quality improvement projects
measure before and after
look at difference
1/2 of randomized trial
no prove cause
SUBJECT SELECTION
well defined
cohort
case control
RCT
matching
accounts for some factor that effects exposure and/ or outcome
fine
generalized block
block randomization (RCT)
STUDY DESIGN QUESTION