Categorical data II

Question 1

Give examples of prospective studies

Answer 1

cohort studies
longitudinal studies
follow-up studies

Question 2

Describe prospective studies

Answer 2

identify individuals with relevant characteristics then follow over time and record eventual outcomes

Question 3

What are caveats for observational studies?

Answer 3

Only able to demonstrate associations between exposure and outcome, rather than causal relationship. A confounding factor may be related to both exposure and outcome seperately

Question 4

Describe cohort studies

Answer 4

most ideal form of observational study
analogous to a clinical trial (without randomisation)
can follow the natural history of disease in time, from exposure to outcomes
Loss to follow up - connected to outcome is problem
Change in exposure / risk over time

Question 5

How is the relative risk calculated?

Answer 5

(a/a+c)/(b/b+d)

Question 6

How are confidence intervals calculated for RR?

Answer 6

logeRR +/- 1.96/SE(logeRR)

Question 7

Describe hypothesis testing for RR

Answer 7

Ho is that RR=1

z = logeRR/SE(logeRR)

Question 8

Describe case-control studies

Answer 8

quicker and cheaper if outcome is rare
selection of controls and matching are issues
recall accuracy

Question 9

Describe the odds ratio

Answer 9

cannot use RR for case-control studies because cases and controls are fixed by study design
OR=ad/bc

Question 10

How is the OR calculated for matched controls?

Answer 10

OR=b/c