Exam 2: Case-control Studies

Question 1

Describe case-control studies

Answer 1

Cases (animals with a disease) that present are compared with one or more controls
For both cases and controls, look back into the past and compare the frequency of occurrence of exposures/risk factors
Can look at multiple risk factors to detect which ones are more (or less) frequently seen in cases and therefore may be causal
Done quickly with low cost
Can be used to study rare diseases

Question 2

What is the measure of association for case-control?

Answer 2

Odds ratio

Question 3

What is an easy way to calculate odds ratio?

Answer 3

Cross product ratio: (ad)/(bc)

Question 4

What does an odds ratio greater than 1 indicate?

Answer 4

An increased risk

Question 5

What does an odds ratio equal to 1 indicate?

Answer 5

There is no increased risk

Question 6

What does an odds ratio less than 1 indicate?

Answer 6

A sparing effect

Question 7

Can relative risk be used in case-control studies?

Answer 7

No

Question 8

What does odds ratio estimate in case-control studies?

Answer 8

risk of exposure in cases compared to exposure in controls

Question 9

What does relative risk estimate in cohort studies?

Answer 9

Risk of disease in exposed compared to risk of disease in non-exposed

Question 10

Look at examples

Answer 10

Look at examples