module 5 probability

Question 1

probability definition

Answer 1

likelihood that an event will occur

Question 2

3 principles of probability

Answer 2

• likelihood of occurrence must be >/0 0 and = 1.
• sum of probabilities must =1
• either of 2 event occurring is the sum of the likelihood of the individual event occurring

Question 3

marginal (simple) probability

Answer 3

number of times the event occurred divided by the total number of times that it could have occurred.

Question 4

conditional probability

Answer 4

probability that one event will occur given that another event has occurred.
- usually compare

Question 5

Joint probability

Answer 5

cooccurrence of two or more events

- words “both” or “and” are used.

Question 6

type 1 error

Answer 6

false positive

Question 7

type II error

Answer 7

false negative

Question 8

sensitivity

Answer 8

probability that the test result is positive when given to a group of patients who have the disease

• pts with the disease will be +
• good for ruling out (SnOut)
• Sn = TP/ (TP + FN)

Question 9

Specificity

Answer 9

probability that the test will be negative among patients who do not have the disease.

• Good for ruling in (SpIN)
• Sp = TN/ (TN + FP)

Question 10

Positive predictive value

Answer 10

probability that a patients who tested positive for a disease actually has the disease.

• ability to rule in; TP in relation to all positives.
• PPV = TP/ (TP + FP)

Question 11

Negative predictive value

Answer 11

probability that a patient who tested negative for a disease really does not have the disease.

• ability to rule-out; TN in relation to all negatives.
• NPV = TN/ (TN + FN)