Feb 4 Study Design

Question 1

Unit of analysis, individual or population, which one is ecological study?

Answer 1

Anything group is ecological study. It is an exploratory approach, and the resutls can;t be applied to indiviudal level, uses extrapolation

Question 2

What is are the 3 types of directionality for observational studies? What type of study does each become?

Answer 2

Have exposure (selecting subjects based on them being exposed, then observe them to determine outcome) = COHORT STUDY

Outcome (select them based on outcome, assess them for presence of exposure) = CASE CONTROL STUDY

None (subject not selected for exposure or outcome) = CROSS-SECTIONAL STUDY

Question 3

What are strengths and weaknesses of cross-sectional studies?

Answer 3

They can estimate the prevalence of disease and exposure, and it cheaper. Can be done retrospectively.

Weaknesses: not for rare diseases or short duration diseases as there is not enough data. CAN’T assess causation. Can’t control any variables

Question 4

What are the strengths and weaknesses of case-control studies?

Answer 4

They are good for rare diseases as select based on outcome, then look for exposures.

Weaknesses: Retrospective, so no causation. Have recall bias.
Can’t estimate incidence/prevalence of the disease

Question 5

What are the strengths and weaknesses of cohort studies?

Answer 5

Follow new cases, so can calculate incidence. Good for rare exposure variables as you select for them.

Weaknesses: Not good for rare diseases as may not see it in subjects. Can’t estimate prevalence of exposure.