formulas

Question 1

What does sensitivity measure?

Answer 1

Sensitivity measures how well a test identifies those with the disease. A high sensitivity means fewer cases are missed.

Question 2

What does specificity measure?

Answer 2

Specificity measures how well a test identifies those without the disease. A high specificity means fewer people without the disease are incorrectly labeled as having it.

Question 3

What is Positive Predictive Value (PPV)?

Answer 3

PPV indicates the chance that someone who tested positive actually has the disease.

Question 4

What is Negative Predictive Value (NPV)?

Answer 4

NPV indicates the chance that someone who tested negative really doesn’t have the disease.

Question 5

What is the attack rate?

Answer 5

The attack rate measures the proportion of people in a population who become ill during a specific time period, typically an outbreak.

Question 6

What is relative risk?

Answer 6

Relative risk compares the risk of disease in a group exposed to a potential risk factor to the risk in a group not exposed to that factor.

Question 7

What is the formula for sensitivity?

Answer 7

Sensitivity = (True Positives) / (True Positives + False Negatives)

a / (a + c)

Question 8

What is the formula for specificity?

Answer 8

Specificity = (True Negatives) / (True Negatives + False Positives)

d / (b + d)

Question 9

What is the formula for Positive Predictive Value (PPV)?

Answer 9

PPV = (True Positives) / (True Positives + False Positives)

a / (a + c)

Question 10

What is the formula for Negative Predictive Value (NPV)?

Answer 10

NPV = (True Negatives) / (True Negatives + False Negatives)

d / (b + d)

Question 11

What is the formula for attack rate?

Answer 11

Attack Rate = (Number of people who became ill) / (Total number of people at risk)

a / (a + c)

Question 12

What is the formula for relative risk?

Answer 12

Relative Risk = (Attack Rate in exposed group) / (Attack Rate in unexposed group)

Question 13

What does high sensitivity indicate?

Answer 13

High sensitivity indicates that the test is good at finding people who have the disease.

Question 14

What does high specificity indicate?

Answer 14

High specificity indicates that the test is good at correctly identifying people who don’t have the disease.

Question 15

What does high PPV indicate?

Answer 15

High PPV means a positive test result is more likely to be a true positive.

Question 16

What does high NPV indicate?

Answer 16

High NPV means a negative test result is more likely to be a true negative.

Question 17

What are the key points of a good screening test?

Answer 17

A good screening test has high sensitivity and specificity, but there’s often a trade-off between the two.

Question 18

What are the components of a contingency table?

Answer 18

True Positives (TP), False Positives (FP), True Negatives (TN), False Negatives (FN).

Question 19

What does sensitivity (True Positive Rate) indicate?

Answer 19

If you have the disease, the test will correctly identify you as positive x% of the time.

Question 20

What does specificity (True Negative Rate) indicate?

Answer 20

If you test positive, there’s a x% chance you actually have the disease.

Question 21

What does Positive Predictive Value (PPV) indicate?

Answer 21

If you test positive, there’s a x% chance you actually have the disease.

Question 22

What does Negative Predictive Value (NPV) indicate?

Answer 22

If you test negative, there’s a x% chance you really don’t have the disease.