Lecture 10 - Relative Risks & Odd Ratios

Question 1

What is the formula for RR (relative risk) ?

Answer 1

RR = Probability of an event in treatment group / Probability of an event in control group

Treatment/Control !!!

Question 2

How do you calculate EER (experimental event rate) ?

Answer 2

EER = treated with disease / (treated with disease + treated with no disease)

Question 3

How do you calculate CER (control event rate) ?

Answer 3

CER = control with disease / (control with disease + control with no disease)

Question 4

RR = ?

Answer 4

RR = EER/CER

Question 5

How do we calculate RRR ?

Answer 5

RRR = [Absolute value (EER - CER)] / CER

RRR = 1 - RR

Question 6

What is the point estimate for CI ?

• if it contains, we accept
• if it doesn’t, we reject

Answer 6

1 ?

slide 14

Question 7

What is ARR??

Answer 7

ARR = absolute value of (EER-CER)

Question 8

NNT ?

Answer 8

NNT = 1/ARR = 1/Abs(EER-CER)

Question 9

NNT are always rounded ____ to the nearest whole number

Answer 9

up

*makes the result more conservative

Question 10

look at slide 35

Answer 10

okay

Question 11

What is the general formula for ODDS RATIO ?

Answer 11

odds ratio = [a/b] / [c/d] = ad/bc

Question 12

What will be closer to 1 ? (RR or OR)

Answer 12

RR

Question 13

If base line risk (risk of events in control group) is low (<30%), the difference between OR and RR is _____ to be important.

Answer 13

unlikely

Question 14

If OR is near ___, the difference between RR and OR is unlikely to be important

Answer 14

1

Question 15

If baseline risk is high, and OR is not near 1, then RR is ?

Answer 15

likely to be appreciably closer to 1 than OR