Measures of Association Flashcards
what are measures of association
provide mathematical assessment of the relationship between a given exposure and outcome of interest
what 2 things do measures of association do
determine if there is an association
measure the strength of the association
what type of studies are MOA used in
analytical
when comparing exposure groups we assume the exposure is not associated with the disease if:
same amount of disease found in a group of subjects that has the exposure and dont have the exposure
when comparing outcome groups we assume the exposure is not associated with the disease if:
same amount of the exposure is found in a group of diseased subjects as non-diseased subjects
why use MOA
to make comparisons
- compare exposure groups
- compare outcome groups
4 types of MOA
odds ratio
relative risk
attributable risk
prevalence ratio
when is odds ratio used
cross-sectional studies
case-control studies
what MOA can be used in prospective studies used to compare outcomes
relative risk (incidence ratio)
attributable risk
- prospective cohort studies
- clinical trials
when is prevalence ratio used
retrospective cohort studies
cross-sectional studies
T/F incidence can be measured in case-control and cross-sectional studies
false
exposure and disease have already occurred
odds ratio
ratio of the odds of exposure in the diseased group to the odds of exposure in the non-diseased group
odds
ratio of number exposed to number not exposed
how do you calculate odds ratio
odds of exposure in the non-diseased group
if OR=1
odds of exposure among cases was equal to that of controls
no association
if OR>1
odd of exposure among cases was greater than that of control
positive association (prob. causal)
if OR
odds of exposure among cases was greater than that of controls
negative association ( possible protective)
T/F OR tells you if there is an association and the magnitude of associate
true
which observational study design compares exposed to non-exposed
cohort
clinical trials
cross-sectional studies
incidence (risk)
measure used to compare the amount of disease that occurs in the exposed and unexposed groups in prospective studies
cumulative incidence (attack rate, risk)
number of new cases at the end of the study divided by population at risk at the beginning of study
relative risk
used to compare the risk (or incidence) of disease that occurs in the exposed and unexposed groups
how do you calculate relative risk
risk of disease in unexposed group
if RR=1
risk in exposed = risk in unexposed
no association
if RR>1
risk in exposed is greater than unexposed
positive association
if RR
risk of disease in exposed is less than risk in unexposed
negative association
attributable risk (AR)
amount of proportion of overall disease incidence in a population or group that can be attributed to a specific exposure
AR interpreted as
% of the overall disease incidence can be attributed to this particular exposure
T/F attributable risk is used to quantify an association
false
used to set priorities in disease control programs
how do you calculate attributable risk
risk exposed
prevalence ratio
measure used to compare the amount of disease that occurred in the exposed and unexposed groups in retrospective studies
prevalence
probability if being diseased
of diseased/ total # exposed
how to calculate prevalence ratio
prevalence of disease in unexposed
PR= 1
no association
PR>1
positive association (possible causal)
PR
negative association (posible protective)
which study design uses odds and OR
case-control
which study design(s) use incidence and RR
prospective cohort
clinical trial
which study design(s) use prevalence and PR
retrospective cohort
T/F there are no measures of exposure or association for case reports/series
true
