Biostatistics

Question 1

risk ratio

Answer 1

ratio of risk in the exposed group (treatment) divided by risk in the control group

Question 2

Risk ratio =1 (or 100%)

Answer 2

no difference in risk of the outcome between the groups

Question 3

Risk ratio >1 ( or >100%)

Answer 3

greater risk of the outcome in the treatment group

Question 4

Risk ratio <1 ( or <100%)

Answer 4

lower risk of the outcome in the treatment group

Question 5

Absolute risk reduction

Answer 5

includes the reduction in risk and the incidence rate of the outcome
(% risk in control group) - (% risk in treatment group)

Question 6

Number needed to treat

Answer 6

number of patients who need to be treated for a certain period of time in order for one patient to benefit
1/ (risk in control) - (risk in treatment) or 1/ARR

Question 7

Odds Ratio

Answer 7

the probability that an event will occur versus the probability tat it will not occur

Question 8

Hazard Ratio

Answer 8

rate at which an unfavorable event occurs within a short period of time

Question 9

OR or HR = 1

Answer 9

the event rate is the same in the treatment and control arms. There is no advantage to the treatment

Question 10

OR or HR >1

Answer 10

The event rate in treatment group is higher than the event rate in the control group; for example, a HR of 2 for an outcome of death indicates that there are twice as many deaths in the group

Question 11

OR or HR < 1

Answer 11

the event rate in the treatment group is lower than the event rate in control group; for example, a HR of 0.5 for an outcome of death indicates that there half as many deaths in the treatment group

Question 12

Sensitivity

Answer 12

describes how effective a test identifies patients with the condition

Question 13

Specificity

Answer 13

describes how effectively a test identifies patients without the condition

Question 14

Intention-to-treat

Answer 14

includes data for all patients originally allocated to each treatment group even if the patient did not complete the trial according to the study protocol

Question 15

Per protocol

Answer 15

conducted for the subset of the trial population who completed the study according to the protocol

Question 16

Case-control study

Answer 16

compares patients with a disease to those without the disease

Question 17

Cohort study

Answer 17

compares outcomes of a group of patients exposed and not exposed to a treatment

Question 18

Cross-sectional study

Answer 18

estimates the relationship between variables and outcomes at one particular time in a defined population

Question 19

Case report and case series

Answer 19

Describes an adverse reaction or a unique condition that appears in a single patient or a few patients

Question 20

Randomized controlled trial

Answer 20

compares an experimental treatment to a control to determine which is better.

Question 21

Parallel RCT

Answer 21

subjects are randomized to the treatment or control arm for the entire study

Question 22

Crossover RCT

Answer 22

patients are randomized to one or two sequential treatments

Question 23

Factorial design

Answer 23

Randomizes to more than the usual two groups to test a number of experimental conditions

Question 24

Meta-Analysis

Answer 24

Combines results from multiple studies in order to develop a conclusion that has greater statistical power than is possible from the individual smaller groups

Question 25

Systemic review article

Answer 25

summary of the clinical literature that focuses on a specific topic or questions