5. MEASURES OF ASSOCIATION Flashcards
1
Q
- Which kind of variables can we relate Exposure and Outcome to?
A
- Exposure is an Independent Variable
- Outcome is a dependent Variable
EXAMPLE:
- exposure to harmful risk factors will lead to a poor
health outcome
2
Q
- Define Exposure.
A
- this is an event, state or behaviour to which a group of
people is exposed - it has an effect on the probability of the outcome
3
Q
- Provide some examples of Exposure.
A
- exposure to the Sun (UV Radiation)
- smoking
- intaking of fruits and vegetables
- physical activity
- oral contraceptive use
- obesity
4
Q
- Define Outcome.
A
- this is an event, state or behaviour
- we hypothesise that is has resulted from an exposure
to some other variable (event, state, behaviour)
5
Q
- Provide some examples of Outcomes.
A
- they are usually a disease
- they can also be a measure related to health and
disease
EXAMPLES:
- obesity
- colorectal cancer
- type 2 diabetes
- cardiovascular disease
- plasma triglyceride levels
(an increase in triglycerides= an increase in blood sugar)
6
Q
- Does this diagram make sense?
A
- yes
7
Q
- Provide labels for the spaces numbered 1-6.
A
- Binary Outcomes
- Existing Cases
- New Cases
- Odds Ratio
- Risk Ratio
- Rate Ratio
8
Q
- Provide labels for the spaces numbered 7-12.
A
- Numeric Outcomes
- Categorical Exposure
- Numeric Exposure
- Mean Difference
- Correlation Coefficient
- Regression Coefficient
9
Q
- What is meant by Binary Outcomes?
A
- you either have the disease or you do not
10
Q
- What is meant by New Cases?
A
- this means that the exposure can happen before the
outcome - this helps with calculating incidence
11
Q
- What are the 3 ways of calculating Binary Outcomes?
A
- Odds Ratio
- Risk Ratio
- Rate Ratio
12
Q
- What do measures of Association assess?
A
- they assess the presence between the magnitude of an
association - this association happens between the Exposure and
the Outcome
NB:
- they assess the change in outcome for a given change
in exposure
- this applies to both numeric and categorical exposures
and outcomes
13
Q
- What does Relative Risk refer to?
A
- it refers to the comparison between two risks
- risks are also known as incidences
IT IS ALSO KNOWN AS:
- as risk in relation to a reference risk
14
Q
- What is Relative Risk a measure of?
A
- it is a measure of association
- it assesses the probability of an event occurring in an
exposed group of people - this is then relative to the probability of the same event
occurring in an unexposed group of people
15
Q
- What are other terms for the following:
15.1. the event occurring
15.2. the exposed group of people
15.3. the unexposed group of people
A
15.1. the risk of the outcome
15.2. this is the numerator in the equation
15.3. the reference
16
Q
- What types of variables are Exposure and Outcome?
A
- they are both categorical
17
Q
- What are the two Measures of Association referred to as Relative Risk?
A
- Risk Ratio
- Rate Ratio
18
Q
- What is Risk Ratio?
A
- this is the ratio of two risks
- this is the ratio of two cumulative incidences
19
Q
- What is Rate Ratio?
A
- this is the ratio of two rates
- this is the ratio of two incidence rates
- the denominator for this is total person time
20
Q
- What is another name for a Rate Ratio?
A
- a Hazard Ratio
21
Q
- In a Relative Risk, which two groups of individuals are compared?
A
- the exposed category
- the unexposed (reference) category
22
Q
- Let’s say the Exposure is smoking status, what is the exposed group and what is the unexposed group?
A
- EXPOSED GROUP:
- smokers
- UNEXPOSED GROUP:
- non-smokers
- this is the reference group
23
Q
- Let’s say the Exposure is Medication type
(a positive exposure), what is the exposed group and
what is the unexposed group?
A
- EXPOSED GROUP:
- those who are taking active medication
- UNEXPOSED GROUP:
- the Placebo group
24
Q
- What happens when there are more than 2 categories in the Categorical Exposure Variable?
A
- we have to decide which category will be treated as the
Unexposed (Reference) Category - all the other categories are then treated as Exposed
Categories - they are then compared to the Unexposed Category
one at a time
25
Q
- Let’s say our exposure is Alcohol consumption, what are out exposed and unexposed groups?
A
EXPOSED:
- heavy consumer
EXPOSED:
- moderate consumer
UNEXPOSED:
- light consumer
- this is the reference against which the other categories
are compared
26
Q
- When we calculate Relative Risk, which category is always compared?
A
- the Exposed Category is always compared to the
Unexposed (Reference) Category - IT IS NEVER THE OTHER WAY AROUND
27
Q
- In which situations are both Risk and Rate Ratio applicable?
A
- in situations where there is a follow up
- these are known as Prospective Studies
- in situations where there are new, certain outcome
cases - rather than existing ones
28
Q
- How do we calculate Risk Ratio?
A
- your numerator is the incidence of the disease in the
group of the exposed - your denominator is looking at your total population
at risk
29
Q
- How do we calculate Rate Ratio?
A
THIS DIFFERS FROM THE RISK RATIO:
- only when looking at the denominator
