Clinical Questions - Biostatistics

Question 1

Sensitivity

Answer 1

A/A+C

Question 2

Specificity

Answer 2

D/B+D

Question 3

Probability

Answer 3

Probability = predictive value. Look at the stem to determine if it is asking for the PPV or NPV

PPV = A/A+B
NPV = D/C+D

Question 4

Attributable Risk

Answer 4

AR = A/(A+B) - C/(C+D)

Question 5

Incidence

Answer 5

Number of new cases/population at risk of the disease within a given timeframe

Question 6

Prevalence

Answer 6

Number of total cases in the population/population at risk of the disease minus dead and cured within a given timeframe

Question 7

Research study that compares a group of people with a given disease to a group without the disease

Answer 7

Case control study - retrospective observational

Question 8

Research study with a given risk factor or exposure to a group without the risk factor

Answer 8

Cohort study - prospective or retrospective

Question 9

Participants are randomly assigned to either the experimental group or the control group

Answer 9

Randomized controlled trial

Question 10

Relative risk

Answer 10

RR = (A/(A+B)) / (C/(C+D))

Question 11

Absolute risk reduction

Answer 11

ARR = C/C+D - A/A+B

Question 12

Number needed to treat

Answer 12

1/ARR

Question 13

Standard error of the mean

Answer 13

SEM = standard deviation / sq rt of sample size

Question 14

Confidence interval

Answer 14

Mean +/- Z (SEM)

CI of 90%: Z = 1.645
CI of 95%: Z = 1.96
CI of 99%: Z = 2.57

Question 15

Z for CI of 90%

Answer 15

1.645

Question 16

Z for CI of 95%

Answer 16

1.96

Question 17

Z for CI of 99%

Answer 17

2.57

Question 18

Individual who experience an adverse outcome have a different likelihood of recalling an exposure than those without the adverse outcome

Answer 18

recall bias

Question 19

Early detection may be confused with an increase in survival

Answer 19

lead time bias

Question 20

The association between an exposure and an outcome is distorted by another variable

Answer 20

Confounding bias

Question 21

Subjects in different arms of a study are systematically treated differently

Answer 21

procedure bias

Question 22

information is distorted by the way it is gathered

Answer 22

measurement bias