Session 3

Question 1

Risk difference

Answer 1

risk (incidence) of disease in one group minus the risk (incidence) of disease in another group

Question 2

Attributable Risk (AR)

Answer 2

(I of exposed- I of unexposed)

IE – IU

Question 3

Background Risk

Answer 3

IU

Question 4

Attributable Risk % among exposed (AR%)

Answer 4

AR/IE

Question 5

Risk difference is sometimes called the ________.

Answer 5

Absolute Risk Reduction (ARR)

Question 6

Absolute Risk Reduction (ARR)

Answer 6

Proportion of patients who were spared an adverse outcome due to treatment
IC-IRX

Question 7

Relative Risk (RR)

Answer 7

risk or probability of an outcome given an exposure (to a risk factor or to a treatment), compared to the risk without the exposure

Question 8

RR

Answer 8

IE/IU
or
IRX/ IC —> for a treatment

Question 9

RR > 1

Answer 9

Exposure or treatment increases risk of disease

Question 10

RR < 1

Answer 10

Exposure or treatment decreases the risk of disease

Question 11

RR = 1

Answer 11

Exposure or treatment don’t increase or decrease the risk of disease

Question 12

Relative Risk Reduction (RRR)

Answer 12

Percentage of baseline risk that is removed a a result of a given therapy

Question 13

RRR

Answer 13

ARR/ IC
or
(IC- IRX)/ IC

Question 14

If you have a low IC, what is the relationship to RRR

Answer 14

Low IC means that you will have a high RRR for any given ARR

Question 15

Baseline risk

Answer 15

IC

Question 16

Alternative way to figure out RRR

Answer 16

1-RR

Same as 1- (lRx/IC)

Question 17

Number Needed to Treat (NNT)

Answer 17

Tells us how many patients need to be treated to prevent one outcome event. It is the reciprocal of the absolute risk reduction.

Question 18

NNT

Answer 18

1/ARR

1/ (1C-1Rx)

Question 19

If the ARR increases the NNT _____.

Answer 19

Decreases

Question 20

Increase in baseline risk (IC) in relation to NNT

Answer 20

NNT decreases