Week 2 Revision

Question 1

What are Observational studies? Tell me more about them.

Answer 1

They are descriptive and analytic. Non-experimental. The distribution or determinants are examined without any attempt by the investigator to influence them.

Question 2

What are Intervention studies? Tell me more about them.

Answer 2

Investigators attempt to influence the outcome.

e.g., randomised controlled trial (RCT)
• randomly assign individuals to
treatment/exposure vs control/no exposure
• aim of randomisation is to ensure that
treatment and control groups are comparable
(differ only on exposure/treatment status)

Question 3

Pros and Cons of intervention studies

Answer 3

Pros
• Excellent for causal inference
• Equal distribution of important factors other
than exposure.

Cons
• Often expensive
• Sometimes impractical/unethical
• Often short term follow up (e.g., 2yrs) so LT
effects unclear
• Rare/delayed effects hard to detect
• Strict inclusion/exclusion criteria, less
representative of general pop