Statistics

Question 1

Probability that a test will correctly identify a True Positive when used on a population with the disease

Answer 1

Sensitivity

Question 2

Sensitivity formula

Answer 2

TP / (TP + FN)

Question 3

Probability that a test will correctly identify a True Negative when used on a population without disease

Answer 3

Specificity

Question 4

Specificity formula

Answer 4

TN / (TN + FP)

Question 5

Probability that someone who tests positive actually has the disease

Answer 5

Positive predictive value

Question 6

Positive predictive value formula

Answer 6

TP / (TP + FP)

Question 7

Probability that someone who tests negative is actually disease free

Answer 7

Negative predictive value

Question 8

Negative predictive value formula

Answer 8

TN / (TN + FN)

Question 9

PPV/NPV relationship to prevalence

Answer 9

PPV is directly correlated with prevalence

NPV is indirectly correlated with prevalence

Question 10

Results obtained due to chance alone

Answer 10

Null hypothesis

Question 11

The chance that the null hypothesis was rejected in error

Answer 11

P value

(Null was correct and the results were due to chance)

Question 12

Type 1 error

Answer 12

Rejected the null hypothesis in error

Same as p value

False positive

Alpha

Question 13

Type II error

Answer 13

Accepted null hypothesis in error

False negative

Beta

Question 14

Number Needed to Treat (NNT)

Answer 14

Number of patients that would need to be treated to prevent one additional adverse effect

1 / ARR

Question 15

Absolute Risk Reduction (ARR)

Answer 15

Rate in untreated group - rate in treated group

OR

rate in treatment A - rate in treatment B

Question 16

Positive likelihood ratio

Answer 16

Sensitivity / (1-specificity)

Question 17

Negative likelihood ratio

Answer 17

1 - Sensitivity / specificity

Question 18

LR > 1

Answer 18

Increases probability that the condition is present

Question 19

LR < 1

Answer 19

Makes condition less likely

Question 20

Absolute Risk

Answer 20

+ disease patients / total patients exposed

Question 21

Relative Risk

Answer 21

Exposed patients (disease/total) / unexposed patients (disease/total)

Question 22

Odds Ratio

Answer 22

Cases (exposed/unexposed) / Controls (exposed/unexposed)

Question 23

Cohort studies

Answer 23

Compare group with exposure to group without (control)

Question 24

Case-control studies

Answer 24

Compare group with disease (case) with group without disease (control)

Analyze for exposure to risk factors

Question 25

Cross-sectional studies

Answer 25

Observational
One point in time