Stats

Question 1

Negative predictive value

Answer 1

Negative predictive value

The probability of not having a disease if tested negative

Negative predictive value = healthy individuals negative for the disease / all individuals tested negative

OR

Negative predictive value = True negatives / (True negatives + False negatives)

Question 2

Positive predictive value

Answer 2

Positive predictive value

The probability of having a disease if tested positive

Positive predictive value = affected individuals positive for the disease / all individuals tested positive

OR

Positive predictive value = True positives / (True positives + False positives)

Question 3

Sensitivity

Answer 3

Sensitivity

The probability of a test being positive when a disease is present.

Sensitivity = affected individuals positive for the test / all affected individuals

OR

Sensitivity = True positives / (true positive + False negatives)

Question 4

Specificity

Answer 4

Specificity

The probability of a test being negative when a disease is not present.

Specificity = healthy individuals negative for the test / all healthy individuals

OR

Specificity = True negatives / (True negatives + False positives)

Question 5

Absolute risk

Answer 5

Absolute risk

The probability of developing a disease over the study period in a cohort study

Absolute risk (AR) = Number of individuals developing disease over the study period / Total number of individuals in the cohort