Term
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Definition
| (# of new cases)/(population at risk) |
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Term
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Definition
| The incidence rate calculated using a period of time during which all of the individuals in the population are considered to be at risk for the outcome. = measure of risk |
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Term
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Definition
# of cases of a disease present @ a specific time / # of persons in the pop. @ that specific time
Proportion |
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Term
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Definition
# of people exposed and became ill / # of people exposed
Proportion |
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Term
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Definition
| Tell us how fast the disease is occuring in population. |
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Term
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Definition
| Tell us what fraction of the population is affected. |
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Term
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Definition
| (# of deaths)/(# of cases) |
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Term
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Definition
- most familiar type of case-control trial
- best when the source cohort is ill-defined or dynamic
- controls can be thought of a sample of the survivors at the end of a follow-up period (a/c)/(b/d) --> OR |
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Term
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Definition
amount of risk attributable to an exposure
CI1 - CI0
where CI1 = cumulative incidence in the exposed and CI0 = cumulative incidence in the unexposed |
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Term
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Definition
| (# of deaths)/(population at risk) |
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Term
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Definition
| Odds of being diseased among the exposed divided by the the odds of being diseased in unexposed. |
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Term
| When is the odds ratio a good estimate of the cumilative incidence ratio? |
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Definition
1) cases are representative of all people with the disease in the population from which the cases are drawn
2) control are representative of all people without the disease in the population
3) the disease being studied is rare (less than 10%) |
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Term
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Definition
| compute measures of association separately for each strata of the confounder |
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Term
| Why is the p-value better (and worse) than hypothesis testing? |
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Definition
| the p-value encorporates the strength of association and role of chance in one number encorporates more data but hides it. |
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Term
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Definition
| Compute summary estimate that is mathematically manipulated to account for differential distributions of the confounder across 2 populations – creates ‘comparable’ rates/risks used primarily for age distributions in populations |
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Term
| 95% Confidence Limit Ratio |
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Definition
| ratio of the 95% confidence limits --if the confidence limits are (0.1 - 2) the ratio would be (2/0.1 = 20) -- it is a measure of the precision of the estimate and lower the better |
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Term
| Properties of a Confounder |
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Definition
1. Must be a cause of the DISEASE or, at least a marker (surrogate) of an actual cause of the DISEASE
2. Must be distributed differently in the EXPOSED and UNEXPOSED (dataset-related phenomenon)
3. Cannot be an intermediate step in the causal pathway between exposure and disease EXPOSURE → Factor A → DISEASE --> a nuisance association; artifact caused by a an incidental correlation between two variables (think maternal age and birth order) |
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Term
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Definition
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Term
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Definition
| Making a generalization about a larger group of individuals (population) on the basis of a subset or sample |
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Term
| Calculating the observed vs expected result on the additive scale |
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Definition
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Term
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Definition
Disease
yes no
Exposed yes a b
no c d
Odds of disease among the exposed= a/b
Odds of disease among unexposed= c/d |
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Term
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Definition
| (odds of disease in exposed)/ (odds of disease in unexposed) |
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Term
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Definition
-The ability to invade a host
- (# infected /# susceptible) * 100 |
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Term
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Definition
-The ability to cause disease
-(#clinical disease /# infected) * 100 |
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Term
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Definition
-The ability to cause severe disease
-Measure of severity
-(#deaths/ # w/disease (cases)) * 100 |
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Term
| Basic Reproductive Rate (Ro) |
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Definition
Ro=BCD
-B is the probability of transmission of a given infection per susceptible contact
-C is the # of potentially infectious contacts per unit time
-D is the duration of infectivity of infected person per unit time |
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Term
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Definition
-If Ro > 1, "epidemic"
-If Ro = 1, "endemic"
-If Ro < 1, "eliminating" or "disappering" |
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Term
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Definition
H = (Ro - 1)/ Ro
= 1 - (1/Ro) |
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Term
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Definition
-Fixed membership
-Once defined and study begins, no one can be added
-Most cohort studies are "closed" |
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Term
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Definition
-Synonym = Dynamic population cohort
-Takes on new members as time passes
-Registries are an open cohort |
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