Lecture 3: Measures Of Association

Question 1

Creating possible alternatives to events that already happened, for example someone got a disease instead of not having had it.

Answer 1

Counterfactual thinking/theory

Counter-to the-facts

Question 2

What assumption does counterfactual theory require?

Answer 2

Assumption of exchangeability

Question 3

What is always in the columns of a 2x2 chart?

Answer 3

Disease/Outcome

Question 4

Absolute differences is found by doing what with frequencies?

Answer 4

Subtracting

Question 5

Relative differences is found by doing what with frequencies?

Answer 5

Dividing

Question 6

True or False:

Absolute differences are always larger than relative differences

Answer 6

False

Absolute is smaller

Question 7

Define ‘risk’

Answer 7

The probability of an outcome in an individual group, exposed or not exposed

Question 8

Is risk considered a proportion or ratio?

Answer 8

Proportion

It is a simple percentage

Question 9

Absolute risk reduction formula

Answer 9

Subtracting the absolute risk of those exposed - AR not exposed

Question 10

Relative risk reduction formula

Answer 10

ARR
——
Absolute Risk of the unexposed

Question 11

What does NNT stand for

Answer 11

Number needed to treat

Question 12

What does NNH stand for?

Answer 12

Number needed to harm

Question 13

Doe we want NNH or NNT to be smaller?

Answer 13

We want NNT to be small

We want NNH to be huge

Question 14

Give an example of NNT

Answer 14

It would take 8 patients on a drug for 1 person to get positive benefits

1 in 8 patients on this drug will get positive benefits

Question 15

How to calculate NNT/NNH?

Answer 15

1 divided by Absolute risk reduction

1
——
ARR

Question 16

how to calculate risk ratio?

Answer 16

risk of outcome in exposed//////risk of outcome non-exposed=placebo

Question 17

The exposure or treatment group of interest, is always in the denominator when calculating risk ratio. T/F

Answer 17

false

always in numerator

Question 18

if risk ratio is >1

Answer 18

the outcome is more likely to occur in the study than in the unexposed group

Question 19

if risk ratio is <1

Answer 19

the outcome is less likely to occur in the study group than the unexposed group

Question 20

if risk ratio = 1

Answer 20

outcomes are equally likely in both groups

Question 21

other names for risk ratio

Answer 21

odds ratio

hazard ratio

Question 22

interpret a RR = 1.53

Answer 22

53% more likely

Question 23

interpret a OR = 2.35

Answer 23

outcome is 2.35 times more likely

Question 24

interpret a HR = 0.75

Answer 24

outcome is 25% less likely to occur

Question 25

when interpreting a RR/OR/HR, there are 3 things you must include in your interpretation…..

Answer 25

1. groups you are comparing
2. direction of your results
3. magnitude

Question 26

visual representation of ratio data, horizontal plot allowing the comparison of multiple ratios and their differences from 1.0

Answer 26

forest plot

Question 27

OR INTERPRETATION: association between baseline characteristics of firearm and pedestrian motor vehicle injury hospitalizations. Reference: white, Hispanic OR = 1.43

Answer 27

hospitalization due to firearm injury or pedestrian motor vehicle injury, is 43% more likely to occur in Hispanic ethnicities than white.

Question 28

Odds is a ……?

Answer 28

ratio

Question 29

define ‘odds’

Answer 29

frequency of an outcome occurring vs. not occurring
or
frequency of exposure vs. frequency of not being exposed
or
occurring/not occurring within one group

Question 30

relate odds calculation to a 2x2 table

Answer 30

A/C or B/D

Question 31

odds ratio calculation formula

Answer 31

odds of exposure in non-diseased

Question 32

how is odds ratio different from odds

Answer 32

odds is within same group

OR; ratio of odds from 2 different groups

Question 33

what is the easiest way to calculate OR?

Answer 33

cross multiply

Question 34

in a 2x2 table: odds of exposure formula

Answer 34

A/C

Question 35

in a 2x2 table: odds of exposure in controls

Answer 35

B/D

Question 36

in a 2x2 table: odds ratio formula

Answer 36

AD/BC

Question 37

when reading a research study, how do you know which 2 groups are being compared?

Answer 37

one of the groups will be listed as a reference or their RR will be = 1.0