ENH 122 Lecture Notes - Lecture 2: Cumulative Incidence, Prevalence
13 Mar 2018
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Document Summary
Determine what would happen to outcome if the exposure were removed. Must be counted over a period of time. Needed to study etiology of disease and to monitor and preventive e orts. Determined by taking measurement on people at one point in time. Ranges b/w 0 & 1 and expressed as % E. g. , ratio of iphones to blackberries, dogs to cats etc. Time is included in denominator (measures freq with which an event occurs in a pop"n) Estimated by observing events among a pop"n during a speci ed time period. Always value b/w 0 and 1 in % # disease free ppl at start of follow up period (cumulative incidence = risk) Time that disease free individuals are observed during follow up (incidence density= rate) Attack rate = risk = cumulative incidence . # new cases of disease during period (i) Pop"n at beginning of the period (n) # who ate food and became ill.
