Theory Flashcards
What is the probability that event A occurs?
P(A)
What is the probability that A OR B happens?
P(A) + P(B), P(A+B), P(AUB)
What is the probability that event A AND B occur?
P(A*B), P(AB), P(A∩B)
What does mutually exclusive events mean?
That A and B cannot occur at the same time. E.g. Male is pregnant.
P(A∩B) = 0
What does independent events mean?
Occurrence of A does not affect the occurrence of B. First patient is male, second patient is a woman.
What does conditional probability mean?
Probability of A given that B has occurred. P(AIB)
E.g. probability that a patient has a headache when having fever
What is the risk of illness if risk factor is present?
a / a+b
Having disease with risk factor / having disease and not having disease with risk factor
Risk of having illness when no risk factor is resent
c / c+d
Having disease without risk factor/ having disease and not having disease without risk factor
What is the risk ratio/ relative risk?
Risk ratio is the probability of an event occurring if a risk factor is present to the probability of an event occurring if a risk factor is not present.
a(c+d) / c(a+b)
What does odds mean?
Odds is how many times the probability of an event occurring is greater than not occurring.
O = P(A) / 1 - P(A)
What is the odds of having an illness if the risk factor is present?
a/b
What is the odds of having an illness if the risk factor is not present?
c/d
What is odds ratio?
The ratio of the odds of an event occurring if a risk factor is present to the odds of an event occurring if a risk factor is not present.
(a/b) / (c/d) = (ad)/(cb)
