# data[].attributes.body
Study population is grouped by outcome

Cases are individuals who have the outcome of interest

Controls are individuals who do not have the outcome of interest

Past exposure status is then determined

# data[].attributes.body
An hypothesis is an educated guess about an

association that is testable in a scientific
investigation

Descriptive data provide information to develop

hypotheses about disease causation

Hypotheses tend to be broad initially and are

then refined as more data are gathered

# data[].attributes.body
Standard diagnostic criteria that must be fulfilled

to identify an individual as a case of a particular
disease

Clinical (laboratory results, symptoms, signs)

Restrictions on individual, place, and time

Ensures that all individuals who are counted as

cases actually (likely) have the same disease

# data[].attributes.body
Study population is grouped by exposure status

Groups are then followed over time to determine if they  develop the outcome of interest

Prospective

Exposure assessed at beginning of study

Followed into the future for outcome

Retrospective

Exposure assessed at some  point in the past

Outcome has already

# data[].attributes.body
Exposure:
Any factor that might influence the risk of disease

Outcome:
Disease or condition, standardised using case definition

# data[].attributes.body
• Exposure and outcome status are determined
at the same time
• “Snapshot” of population being studied
• Also includes most opinion and political polls
• Can be descriptive and analytical design
• Investigate the association between a putative risk factor     and a health outcome
• Risk factors and outcome are measured simultaneously
• Difficult to determine whether the exposure proceeded or followed the disease
• Limited ability to draw conclusions about association between a risk factor and health outcome