Editing Epidemiology (section)

==== Information bias ====
[[Information bias (epidemiology)|Information bias]] is bias arising from systematic error in the assessment of a variable.<ref name=Rothman2002>{{cite book|last1=Rothman|first1=K.|title=Epidemiology: An Introduction|url=https://archive.org/details/epidemiology00kenn|url-access=registration|date=2002|publisher=[[Oxford University Press]]|location=Oxford|isbn=978-0195135541}}</ref> An example of this is recall bias. A typical example is again provided by Sackett in his discussion of a study examining the effect of specific exposures on fetal health: "in questioning mothers whose recent pregnancies had ended in fetal death or malformation (cases) and a matched group of mothers whose pregnancies ended normally (controls) it was found that 28% of the former, but only 20% of the latter, reported exposure to drugs which could not be substantiated either in earlier prospective interviews or in other health records".<ref name="Sackett D. Bias in analytic research. J Chron Dis 1979; vol. 32:51–63." /> In this example, recall bias probably occurred as a result of women who had had miscarriages having an apparent tendency to better recall and therefore report previous exposures.