Session 1 Flashcards
Conditional Probabilities
The probability of one condition given another specified condition
Disease Odds Ratio
The odds of disease in the exposed divide by the odds of disease in the unexposed (the odds are the probability of disease divided by its complement)
Exposure Odds Ratio
The odds of exposure among cases divided by the odds of exposure in controls. (The odds are the probability of exposure divided by its complement).
Note: The exposure odds ratio and the disease odds ratio are equivalent although the disease odds are not equivalent to the exposure odds. (The ORs are equivalent but the complements of the ORs are not)
Incidence Rate
The number of new cases of disease per observed unit of disease-free person-time
Odds
A probability divided by its complement. Incidence odds - the risk divided by its complement (1- the risk) - is known as Cornfield’s odds ratio.
Person-time
The total amount of time the individuals in a cohort are observed while at risk for developing the disease (observed while disease-free)
Prevalence
A measure of extant disease, regardless of timing of onset or present of past episodes. The proportion of individuals in a population with disease at a particular moment in time. (Existing cases)
Rate
“Instantaneous force of disease occurrence.” A measure of how quickly people in a population change status from non-diseased to diseased.
Rate Ratio
The ratio of the incidence rate in the exposed to the incidence rate in the unexposed.
Risk
The probability of developing the disease over a designated time period; the proportion of disease-free individuals in a fixed cohort who develop disease by the end of a designated time period (average risk)
Risk Difference
The difference between the risks in the exposed and the unexposed.
Risk Ratio
The ratio of the risk in the exposed and the unexposed
