Lecture 8 9/4/24

Question 1

What is positive predictive value?

Answer 1

post-test probability of having a disease after a positive test result

Question 2

What is negative predictive value?

Answer 2

post-test probability of not having a disease after a negative test result

Question 3

What is inverse negative predictive value (1-NPV)?

Answer 3

post-test probability of having a disease after a negative test result

Question 4

How is positive predictive value calculated?

Answer 4

true positives that test positive/total test positives

Question 5

How is negative predictive value calculated?

Answer 5

true negatives that test negative/total test negatives

Question 6

How is inverse negative predictive value (1-NPV) calculated?

Answer 6

false negatives/total test negatives

Question 7

What is a likelihood ratio?

Answer 7

ratio of the probability of a test result among diseased individuals to probability of that test result among non-diseased individuals

Question 8

How is a positive likelihood ratio interpreted?

Answer 8

a positive test result is xx times as likely in a disease positive animal than a disease negative animal (xx typically a large number)

Question 9

How is a negative likelihood ratio interpreted?

Answer 9

a negative test result is xx times as likely in a disease positive cat than a disease negative animal (xx typically a small number)

Question 10

What is a type I/alpha error?

Answer 10

false positive error, in which disease is concluded to be present when it is not

Question 11

What is a type II/beta error?

Answer 11

false negative error, in which disease is concluded not to be present when it is

Question 12

How is type I/alpha error calculated?

Answer 12

false positive tests/total true negative cases, or 1 - specificity

Question 13

How is type 2/beta error calculated?

Answer 13

false negative tests/total true positive cases, or 1 - sensitivity