Case-control Studies

Question 1

What are the Bradford hill criteria?

How many are there?

Answer 1

X9 criteria for establishing a causal realtionship

1) strength of association
2) consistency
3) specificity
4) temporality
5) dose response relationship
6) biological plausibility
7) coherence
8) experimental existence
9) analogy (alternate explanations)

Question 2

What happens if you increase the number of controls per case?

Answer 2

You increase the study power

Question 3

What is study power?

Answer 3

The probability of detecting an effect if it is truly there

Question 4

In case-control studies we use odds ratios, what is an odds ratio?

How is it calculated?

Answer 4

It is how many times more or less likely the odds are in finding a exposure in someone with the disease

= (a x d) / (b x c)

Question 5

If a CI is calculated for an OR, what X2 things should you look for?

Answer 5

1) all values above or below 0 (0 not included in the range)

2) a p-value of <0.05

Question 6

What is the RR?

Answer 6

How many times more or less likely an exposed person is to getting the disease.

Question 7

What is a counfounder?

Answer 7

A factor associated with the exposure and independently with the disease which can confuse a study to make it appear that an exposure has more/less of an effect on the outcome