Amazon.com description: Product Description: The guidelines in this report deal only with observational data on human health, for example, those that are obtained in ecologic, cross-sectional, case-control, and cohort studies. Since the activities of the National Center for Health Statistics traditionally have centered around population surveys rather then to other types of studies, such as case-control or cohort studies. Publication of these initial guidelines is expected to elicit comments and contributions from experts in the latter areas, which can then be incorporated in subsequent versions. These guidelines are not meant to serve as a comprehensive manual on conducting observational studies.