# Week 2 lecture notes.docx - Learning Objectives To define...

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Learning Objectives To define and provide examples of a population To distinguish between a fixed and dynamic population To describe the key aspects of measuring disease occurrence To define and distinguish among prevalence, cumulative incidence, and incidence rate To describe the mathematical relationship among the measures of disease frequency To calculate and interpret commonly used measures of disease frequency in public health To know how to calculate person-time To organize disease frequency data into a two-by-two table To describe and calculate absolute and relative measures of comparison including rate/risk difference, population rate/risk difference, attributable proportion between the exposed and total population, and the rate/risk ratio (relative risk) To be able to interpret each absolute and relative measure of comparison To describe the purposes of rate standardization and calculate the directly- adjusted standardized rate, and SMRs using indirect standardization disease frequency in populations through the calculation of rates, we have to actually measure the frequency of disease in a population before we can look at its distribution geographically or by other factors helps identify patterns of disease and also disease trends in a population as they occur short-term and long-term trends are all based upon the calculation of rates A population in general is a group of persons with a common characteristic range from living in the same city, to being born in the same year, to being in the same classroom there are some rates that are more appropriate to a fixed population and some rates more appropriate to a dynamic population fixed population once you're in that population, you're in it forever until you essentially exit it through death Examples members of the Framingham cohort study of Massachusetts, persons who were living around the Chernobyl reactor in Ukraine in 1986 and were exposed to radiation, and also individuals living in Hiroshima and Nagasaki, Japan, and were exposed to the atomic bombings in both cities. Their exposure fixed them in those two populations forever dynamic population more common people enter and leave - birth, deaths, migration, immigration. It's in constant flux/changing o Ex. the population of most countries or most cities or most states are defined as dynamic populations the mechanics of actually how we calculate rates in a population need three pieces of information
1. a numerator, the number of cases of a particular disease that occurs in a population 2. a number of the population itself, or a denominator 3. need to account for that time to the calculation of person time - in the case of the only true rate, an incidence rate, a function of time, or a person time, because the rate of disease changes as a person moves through time Three Types of Frequency Measures Used to relate number cases of disease, size of population, and time.
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