Statistics 2

Question 1

What are the different types of observational study?

Answer 1

-Cohort study
-Case control
-Cross-sectional

Question 2

What is the time scale of cohort studies?

Answer 2

-They look forwards into the future
(Information on disease outcomes)

Question 3

What is the time scale of case control studies?

Answer 3

-They look into the past
(Subjects asked to recall information on past exposures)

Question 4

What is the time scale of cross sectional studies?

Answer 4

-They happen in the present
(Collect information on exposures and diseases at the same time e.g. using questionnaire)

Question 5

What is the meaning of reverse causality?

Answer 5

-Disease status influences exposure status rather than exposure status influencing disease status
-E.g. Once people diagnosed with IHD, they start consuming more Vitamin C. This does not mean that more Vitamin C consumption causes IHD

Question 6

What is the formula for expected frequency in a 2x2 contingency table?

Answer 6

(row total x column total) / grand total

Question 7

What is the time scale of cross sectional studies?

Answer 7

-They happen in present
Collect information on exposures and diseases at the same time