Statistics

Question 1

Define relative risk

Answer 1

The incidence in the exposed group divided by the incidence in the non- exposed group

Question 2

Absolute risk definition

Answer 2

Incidence of the disease in the exposed group

Question 3

Relative risk values meaning

Answer 3

RR= 1 means no difference between 2 groups so no association

RR>1 means increased occurrence in exposed group so it is a positive association/ risk factor

RR <1 means decreased risk = negative association = protective effect

Question 4

Odds ratio

Answer 4

Used in case- control studies

Assesses the odds that an individual with a specific condition has been exposed to something

Question 5

Define sensitivity

Answer 5

The ability of a test to detect a disease
Ie the chance of the test being positive if you have the disease

Good for ruling things out. A highly sensitive test has few false negatives so if negative test, it’s very unlikely you have the disease

Question 6

Define specificity

Answer 6

The ability of a test to identify those without the disease
Change of the test being negative if you don’t have the disease

Good for ruling things in- a highly specific test will have few false positives so if the test is positive you are very likely to have the disease

Question 7

Positive predictive value

Answer 7

Likelihood that someone with a positive test actually has the disease

Question 8

Negative predictive value

Answer 8

Likelihood that someone with a negative test actually does not have the disease

Question 9

Predictive values and prevalence

Answer 9

PV closely related to prevalence. A pt with a positive test is more likely to truly have the disease if the patient belongs to a population with a high prevalence of disease ie high pretest probability