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30 Cards in this Set

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Disease Association
present when exposure occurs together with the outcome more often than chance

association ≠ causation
Incidence of Disease Among Exposed Cases
= a / (a + b)

a = cases of dz in exposed cases
b = cases of no dz in exposed cases
Incidence of Disease Among Unexposed Cases
= c / (c + d)

c = cases of dz in unexposed cases
d = cases of no dz in unexposed cases
Absolute Risk
1) incidence of dz in exposed pop'n
= a / (a + b)

2) incidence of dz in total pop'n
= (a + c) / (a + b + c + d)

* does not indicate if exposure is associated with INCREASED risk of disease
Risk Difference
dz risk in exposed - dz risk in unexposed

= [a/(a+b)] / [c/(c+d)]

how much greater on an abs scale is the freq of dz in one group compared to other
Relative Risk Ratio
dz risk in exposed / dz risk in unexposed

= [a/(a+b)] / [c/(c+d)]

how much more LIKELY one group will develop dz releative to other

* can't assess incidence using relative risk
Cumulative Incidence Ratio (Risk Ratio)
cumulative incidence for exposed / cumulative incidence for unexposed
Incidence Density Rate (Rate Ratio)
incidence density of exposed / incidence density of unexposed
Prevalence Ratio
disease prevalence for exposed / disease prevalence for unexposed
Risk
probability of developing an outcome over a specified period of time

* based on a proportion

- numerator: number of times outcome occurs during the study

- denominator: total number of times outcme could have occurred

* cannot estimate risk directly from case-control study
Odds that Case was Exposed
= a/c
Odds that Control was Exposed
= b/d
Odds Ratio
odds that a case was exposed / odds that a control was exposed

= (a * d) / (b * c)
Interpreting Magnitude and Direction of RR and OR
1) RR = 1, OR = 1
- no association

2) RR > 1, OR > 1
- exposed group has more dz than unexposed
- regarded as risk factor

3) RR < 1, OR < 1
- exposed group has less dz than unexposed
- protective factor
RR vs OR
* RR estimates association btw exposure and dz in exposed relative to unexposed

* OR is the ratio of the odds that cases were exposed relative to the odds that controls were exposed
Disease Association
present when exposure occurs together with the outcome more often than chance

association ≠ causation
Incidence of Disease Among Exposed Cases
= a / (a + b)

a = cases of dz in exposed cases
b = cases of no dz in exposed cases
Incidence of Disease Among Unexposed Cases
= c / (c + d)

c = cases of dz in unexposed cases
d = cases of no dz in unexposed cases
Absolute Risk
1) incidence of dz in exposed pop'n
= a / (a + b)

2) incidence of dz in total pop'n
= (a + c) / (a + b + c + d)

* does not indicate if exposure is associated with INCREASED risk of disease
Risk Difference
dz risk in exposed - dz risk in unexposed

= [a/(a+b)] / [c/(c+d)]

how much greater on an abs scale is the freq of dz in one group compared to other
Relative Risk Ratio
dz risk in exposed / dz risk in unexposed

= [a/(a+b)] / [c/(c+d)]

how much more LIKELY one group will develop dz releative to other

* can't assess incidence using relative risk
Cumulative Incidence Ratio (Risk Ratio)
cumulative incidence for exposed / cumulative incidence for unexposed
Incidence Density Rate (Rate Ratio)
incidence density of exposed / incidence density of unexposed
Prevalence Ratio
disease prevalence for exposed / disease prevalence for unexposed
Risk
probability of developing an outcome over a specified period of time

* based on a proportion

- numerator: number of times outcome occurs during the study

- denominator: total number of times outcme could have occurred

* cannot estimate risk directly from case-control study
Odds that Case was Exposed
= a/c
Odds that Control was Exposed
= b/d
Odds Ratio
odds that a case was exposed / odds that a control was exposed

= (a * d) / (b * c)
Interpreting Magnitude and Direction of RR and OR
1) RR = 1, OR = 1
- no association

2) RR > 1, OR > 1
- exposed group has more dz than unexposed
- regarded as risk factor

3) RR < 1, OR < 1
- exposed group has less dz than unexposed
- protective factor
RR vs OR
* RR estimates association btw exposure and dz in exposed relative to unexposed

* OR is the ratio of the odds that cases were exposed relative to the odds that controls were exposed