Exam 2

Question 1

Experimental Event Rate

Answer 1

a/(a+b) x 100

Question 2

Control Event Rate

Answer 2

c/(c+d) x 100

Question 3

Relative Risk Reduction

Answer 3

(CER - EER) / CER

Question 4

Absolute Risk Reduction

Answer 4

CER - EER

Question 5

Number Needed to Treat

Answer 5

1/ARR

Question 6

Relative Risk

Answer 6

EER/CER = a(c+d) / c(a+b)

Question 7

Odds Ratio

Answer 7

ad/bc

Question 8

Explain the 2 X 2 table

Answer 8

Vertical columns = diseased, not diseased
Horizontal rows = treated, control
a = treated group, diseased
b = treated group, not diseased
c = control, diseased
d = control, not diseased

Question 9

Define sensitivity, give equation (screening test)

Answer 9

probability of having a positive test if you have the disease
TP / (TP + FN) a/(a+c)

Question 10

Define specificity, give equation (confirmatory test)

Answer 10

probability of having negative test if you don’t have disease
TN / (TN + FP); d/(d+b)

Question 11

Define Positive predictive value, give equation

Answer 11

probability of having disease given a positive test

TP/ (TP + FP); a/(a+b)

Question 12

Define Negative Predictive Value, give equation

Answer 12

probability of not having disease when given a negative test

TN / (TN + FN); d/(d+c)

Question 13

Positive Likelihood ratio (likelihood of having disease)

Answer 13

Sensitivity / (1 - specificity)

Question 14

Negative likelihood ratio (likelihood of not having disease)

Answer 14

(1 - sensitivity) / specificity