Formulas

Question 1

Relative Risk formula

Answer 1

EER/CER

Question 2

Relative risk inc/reduction formula

Answer 2

1-RR

Question 3

ARD formula

Answer 3

CER-EER

Question 4

NNT formula

Answer 4

1/ARD

Question 5

Prevalence formula

Answer 5

a+c/a+b+c+d

all positives / all

Question 6

what is used to measure Pre-test probability

Answer 6

usually = prevalence

Question 7

Sensitiivity formula

Answer 7

a/(a+c)

true positives/all disease positives

Question 8

specificity formula

Answer 8

d/(b+d)

true negatives/all disease negatives

Question 9

What is the purpose of sensitivity?

Answer 9

“SnOut” - rule out a diagnosis

-more sensitive test confirms the accuracy of a negative result

Question 10

what is the purpose of specificity?

Answer 10

“SpIn” Rules in a diagnosis
rules in the diagnosis

-more specific test rules in a positive test result

Question 11

positive predictive value formula

Answer 11

a/a+b

true positive/all test positives

Question 12

negative predictive value formula

Answer 12

d/c+d

true negatives/ all test negatives

Question 13

How do sensitivity and specificity change with the prevalence?

Answer 13

they DON’T

Question 14

likelihood ratio for positive formula

Answer 14

sensitivity /1-specificity

Question 15

likelihood ratio for negative formula

Answer 15

1-sensitivity/specificity

Question 16

Do you want to minimize or maximize the area under the curve?

Answer 16

maximize

Question 17

Odds ratio formula

Answer 17

OR = ad/bc

Question 18

What does the following values for odds ratio mean:

OR=1
OR>1
OR<1

Answer 18

OR=1 -exposure doesn’t affect outcome

OR>1 = exposure associated with higher odds of outcome

OR<1 = exposure associated w/ low risk of outcome