1. Comparison of three Observational Analytical strategies
Attribute
Cohort
Case-control
Cross-sectional
Classification of population
Population free from condition or disease
Cases with condition or disease with or without the characteristic, and controls
Populations without- identification of condition or characteristic
Sample represented
Non-diseased
Uncertain: the source population of the cases
is unknown
Survivors at a point or period in time
Temporal sequence
Prospective or Retrospective
Retrospective
Contemporary or
retrospective
Function
Compares incidence rates in exposed and unexposed
Compares prevalence of exposure among cases and controls
Describes association between exposure and disease simultaneously

2. Comparison of three Observational Analytical strategies
Attribute
Cohort
Case-control
Cross-sectional
Outcome
Incidence of disease
in exposed and
unexposed
Prevalence of exposure in cases and controls
Prevalence of disease
in exposed and unexposed
Risk measure
Relative risk,
attributable risk
Odds ratio (estimate of relative risk)
Prevalence ratio
(inexact estimate of
relative risk); also
odds ratio
Evidence of causality
Strong
Needs more careful
analysis
Only suggestive
Bias
Easy to manage
Needs more effort and sometimes very difficult
to manage
May be very difficult to
manage