NCHS statistical and analytic data information products are used extensively to evaluate and profile the health of the American people. Often, findings from NCHS surveys serve as benchmarks for investigating the need to modify or implement policies that will affect initiatives addressing specific health concerns of the United States population or specific health concerns of certain population sub-groups. In recognition of the potential impact some of its statistical and analytic data products may have on health policy and initiatives, NCHS requires that these products meet the highest possible quality standards. In order to accomplish this goal, quality standards are embedded throughout all survey processes and procedures, beginning with the conceptualization and design of a survey, through to data dissemination. The appropriateness of many of these standards is measured by independent assessments (e.g., peer review) conducted by qualified persons. Further, NCHS strives to assure that its processes and procedures are appropriate, well documented, and capable of being replicated by qualified persons outside of NCHS in order to derive results consistent with those obtained by NCHS. Whenever confidentiality restrictions preclude the general availability of NCHS data sets, methodologies, etc., NCHS makes every effort to provide qualified researchers limited access to confidential files through its Research Data Center, which was established specifically for that purpose.