Confidence Interval

Question 1

Describe the confidence interval

Answer 1

Every study will have a measure of error which is what CI accounts for.
The error comes from the fact that a sample of the population is generalised to the general population

Question 2

What does it mean if 1 lies in the Confidence interval or odds ratio?

Answer 2

It is not statistically significant (P>0.05)

Question 3

How does increasing the population size affect confidence interval?

Answer 3

Decreases CI

Question 4

What does 95% CI for RR above is 0.66-0.85 mean?

Answer 4

This means that we are 95% sure the true relative risk (true value if we studies the population) lays between 0.66-0.85.
e.g. we are 95% sure that statin will reduce stroke risk by at least 15% and at most 34%.

Question 5

What is number needed to treat?

Answer 5

Number of people needed to treat in order to prevent disease in one person

Question 6

Equation for cases that can be avoided

Answer 6

% incidence of intervention group - % incidence in control group