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epidemiology
1/12/98

practice problem day: there IS 
information in these sheets that we need to know and that is ONLY 
presented in these sheets. These sheets are very, very similar to the 
problems we may get on the exam. Is that clear? There are two kinds of 
problems: page one, a set of short answer questions; page two, math 
problems. You should use the first page as a study aid later. Today, do 
the math on p 2 and 3. we'll get a set of answers next class. will not 
have to do confidence intervals on the exam, btw, and will not have to 
know the formulas for confidence intervals.

1)	a) prevalence: the 
proportion of the population that has the disease at one specific point 
in time.
	b) incidence: the instantaneous per capita rate of disease 
occurrence.
	c) cumulative incidence: the proportion of a group of 
disease free animals which eventually develops a disease over a specified 
period of time.

2) what two properties of incidence can be used to 
distinguish it from prevalence? incidence is a rate - units are per time; 
and it is instantaneous

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