Age: a truly confounding variable.
As Hinshaw (1981) has noted, the process of designing research might best be conceptualized as a series of informed decisions that involve constant trade-offs and compromise. With each advantage gained by a particular theoretical or methodological decision, the researcher inherits a certain number of threats to the study's internal and external validity and a potential number of error sources. Because of the nature of the research questions of interest to nurses and because of situational and contextual constraints in the clinical setting, nurse researchers often are required to select samples that contain small or large proportions of elderly subjects. The purpose of this article has been to raise some of the theoretical and methodological issues associated with the selection of both age-heterogeneous samples and age-homogeneous samples. Although in research all possible error sources cannot be controlled, it is possible to reduce the amount of error by a clear understanding of the implications of choices regarding age-related issues and inclusion of design features that reduce the amount of error introduced when research subjects who are relatively young are studied along with research subjects who are elderly.
Phillips
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D000328:Adult; D000368:Aged; D000375:Aging; D006801:Humans; D008875:Middle Aged; D015399:Nursing Research; D012107:Research Design; D012494:Sampling Studies