Measures of Association Flashcards
Any relationship btwn 2 measured quantities that renders them dependent is…
an association (ass.)
What does a dependent (associated) relationship mean?
when one quantity changes, so does the other
What does an independent relationship mean?
when one quantity changes, the other does not change
Measures of association are used to make comparisons between…
- exposure groups
2. outcome groups
What tests are used to measure associations?
Odds ratio
Relative risk (incidence ratio)
Attributable risk
Prevalence ratio
Retrospective studies comparing exposure in diseased groups utilize what test in what scenarios?
Retrospective studies: Cross-Sectional and Case-Control
Utilize Odds Ratio
Prospective studies comparing disease in exposure groups utilize what tests in what scenarios?
Prospective studies: Pros. Cohort and Clinical Trials
Utilize Relative risk and Attributable Risk
Retrospective studies comparing disease in exposure groups utilize what test in what scenarios?
Retrospective studies: Retro. Cohort and Cross-Sectional
Utilize Prevalence Ratio
How do you calculate the odds ratio?
Odds of exposure in the diseased/ odds of exposure in the non-diseased
If the OR = 1…
the odds of exposure among cases was equal to that of the controls
No association!
If the OR >1…
Odds of exposure among cases was greater than that of controls.
Positive association, possibly causal!
If the OR
Odds of exposure among cases was less than that of controls.
Negative association, possible protective.
What does the Odds Ratio tell you?
OR tells you if there is an association and the magnitude of the association.
The Relative Risk is used to compare…
the Risk (incidence) of disease that occurs in the exposed and unexposed groups.
It is the ratio of incidence of disease in the exposed to the incidence of disease in the unexposed.
How do you calculate Relative Risk (RR)?
Risk (incidence) of disease in the Exposed/ Risk (incidence) of disease in the Unexposed
If RR = 1…
the risk of disease in the exposed group = the risk of disease in the unexposed group –> no association
If RR > 1…
the risk of disease in the exposed group is greater than the risk of disease in the unexposed group
Positive association, possibly causal
If RR
the risk of disease in the exposed group is less than the risk of disease in the unexposed group
Negative association, possibly protective
How do you calculate Incidence Density?
new cases at the end of the study/ animal-time at risk
What is attributable risk?
the amount or proportion of overall disease incidence in a pop. or group that can be attributed to a specific exposure
T/F - Attributable risk is used to set priorities in disease control programs.
False - attributable risk is not usually used to set priorities in disease control programs
Estimating the amount of disease caused by an exposure allows…
estimation of the value of preventing or blocking the exposure
How do you calculate attributable risk?
[Risk(exposed) - Risk(unexposed)] / [Risk(exposed)]
The prevalence ratio is used to compare..
the prevalence of disease in the exposed and the prevalence of disease in the unexposed groups in retrospective studies
How do you calculate the prevalence ratio?
Prevalence of disease in the exposed/ prevalence of disease in the unexposed
If the PR = 1…
the prevalence of disease in the exposed group = prevalence of disease in the unexposed group
no association
If the PR is > 1…
The prevalence of disease in the exposed group is greater than the prevalence of disease in the unexposed group
positive association, may be causal
If the PR is
The prevalence of disease in the exposed group is less than the prevalence of disease in the unexposed group
negative association, possibly protective
Study Design: Clinical Trials
Measure of Dz/Exposure:
Measure of Ass.:
Clinical Trials
Incidence
Rel. Risk
Study Design: Ecologial
Measure of Dz/Exposure:
Measure of Ass.:
Ecological
Various
Various
Study Design: Cross-Sectional
Measure of Dz/Exposure:
Measure of Ass.:
Cross-Sectional
Prevalence/Odds
Prev.Ratio/OR
Study Design: Prospective Cohort
Measure of Dz/Exposure:
Measure of Ass.:
Prospective Cohort
Incidence
Rel.Risk, IR, AR
Study Design: Retrospective Cohort
Measure of Dz/Exposure:
Measure of Ass.:
Retrospective Cohort
Prevalence
Prev.Ratio
Study Design: Case Series
Measure of Dz/Exposure:
Measure of Ass.:
Case Series
None
None
Study Design: Case Report
Measure of Dz/Exposure:
Measure of Ass.:
Case Report
None
None
Study Design: Case Control
Measure of Dz/Exposure:
Measure of Ass.:
Case Control
Odds
OR
