POPM 3240 Lecture Notes - Lecture 4: Relative Risk, Prevalence, Unit
20 Jan 2017
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Unit 4: measures of association and disease frequency. Counts a simple representation of a number of events/outcomes of interest: eg: 1, 3, 75, 2000. Ratios a dimensionless, unit-less comparison of one count to another: eg: 1:4, 2:75. Proportions ratio where number is included in the denominator: eg: 1/100, 27%, 0. 55. Risks proportions that express the probability that something will occur: eg: 1/100, 27%, 0. 55. Rates expresses occurrence of an event/outcome in defined population in a specified period of time: ca(cid:374) (cid:271)e (cid:272)o(cid:374)sidered a (cid:373)easure of (cid:858)speed(cid:859, eg: 1 infection per 100 person-years, 5 deaths per 1000 cow-decades. Approximate denominator (# new cases in population during specified time period)/(nari + narf / 2) x (itc: only have summary data available for a group. Number of new cases among those at risk in a population: 2. Number of new cases within a specific time period. Critical element is defining incidence rate is new cases of disease.
