Statistics

Question 1

How are confidence intervals interpreted?

Answer 1

95% probability of containing the true population mean.
95% of such confidence intervals with contain the true population mean if repeated random samples are taken.
This interval contains the value of the true RR with 95% confidence.
We may be 95% confident that the RR is not 1.

Question 2

What is relative risk and in what type of study is it used?

Answer 2

Risk in exposed/risk in non-exposed = a/a+b divided by c/c+d
USED in a COHORT STUDY

Question 3

What is odds ratio and in what type of study is it used?

Answer 3

Used in a case control study when the incidence in either population = ad/bc.

Question 4

When does the odds ratio approximate relative risk?

Answer 4

1. The cases are representative of all the people with the disease from which the cases were drawn
2. The controls are representative of the population from which the cases were drawn
3. The disease is infrequent.