Equations

Question 1

What is the equation for sensitivity?

Answer 1

a/ (a+c)

Number of true positives / total with disease

Question 2

What is the equation for specificity?

Answer 2

d / (b+d)

number of true negatives / total without the disease

Question 3

What is the equation for Positive predictive value?

Answer 3

a (a+b)

Number of true positive / total number of positives

Question 4

What is the equation for negative predictive value?

Answer 4

c/ (c+d)

Number of true negatives / total number of negatives

Question 5

What is the equation for positive likelihood ratio?

Answer 5

sensitivity / 1- specificity

Question 6

What is the equation for negative likelihood ratio?

Answer 6

1-sensitivity / specificity

Question 7

What is the equation for pretest odds?

Answer 7

prevalence / 1-prevalence

Question 8

What is the equation for post-test odds?

Answer 8

pretest odds *(LR)

Question 9

What is the equation for post test probability?

Answer 9

Post test odds / post test odds + 1