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National Center for Health Statistics: Notice of Sample Size Changes

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Centers for Disease Control and Prevention, Department of Health and Human Services.




The National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention, has provided statistics on the health of the American people for almost 50 years. Two of its preeminent surveys, the National Health Interview Survey and the National Health and Nutrition Examination Survey are at the half century mark. The quality of NCHS' statistical program is of critical concern to the Center. Data on sample design, data quality and estimation techniques are discussed in detail in NCHS reports and in the proposed data collections that are published in the Federal Register and submitted to the Office of Management and Budget (OMB) for review and approval.

The timelines for preparing and submitting requests for OMB approval under the Paperwork Reduction Act and for the Federal Government's budget process often are not synchronized. Thus it is possible that a survey may receive OMB approval for collection of data from a certain number of respondents before the necessary resources have been appropriated in the federal budget. In all cases, the design of the survey allows for changes to the number of respondents without jeopardizing the representativeness of the weighted survey results. In addition, information on final sample sizes is included with each data release.

Over the last decade NCHS has made a number of program changes to stay within existing resources, including changes to survey design and sample size, in order to continue carrying out its mission and maintain its program quality. Three surveys have had or may have sample size reductions take place in FY 2009 and FY 2010. They are the National Health Interview Survey, the National Hospital Discharge Survey and the National Health and Nutrition Examination Survey.

The National Health Interview Survey

The National Health Interview Survey (NHIS) is an in-person household-based survey. The sample design that was in place from 1995 through 2005 called for a sample of 39,000 households and 100,000 individuals. However, in 2002, 2003, and 2004, the sample was reduced on average to approximately 36,000 households and approximately 93,000 individuals.

The sample design implemented in 2006 called for a permanent one-eighth reduction in sample size. However, from 2006-2008, existing resources necessitated a further reduction in sample size down to about 29,000 households and about 76,000 individuals (see table below). The present plan is to reduce the 2009 NHIS to a sample size of about 17,000 households and 43,600 sample persons. All attempts will be made to reinstate the original sample design; however, final decisions on the implementation of the 2010 survey are contingent on available resources.

Table 1—Counts of Interviewed Persons and Households in the 2000-2010 NHIS

Year200020012002200320042005200620072008 expected2009 with a 50% cut2010 with a 50% cut
No. of persons100,618100,76193,38692,14894,46098,64975,71675,76475,50043,58943,589
No. of households38,63338,93236,16135,92136,57938,50929,20429,26629,00016,84816,848

The National Hospital Discharge Survey

The National Hospital Discharge Survey (NHDS) is an establishment-based survey of inpatients discharged from a nationally-representative sample of hospitals. It has been fielded continuously since 1965 with a planned redesign for 2010 pending the results of pretesting the new design elements. With existing resources, it was decided to reduce the sample size by approximately one-half for both hospitals and patients for 2008. Present plans are to finish data collection for the 2008 survey but not to field the 2009 survey. Decisions on the 2010 survey and the implementation of the redesign are contingent on available resources and the results of the pretest.

The National Health and Nutrition Examination Survey

The National Health and Nutrition Examination Survey (NHANES), a nationally-representative survey involving both an interview and physical examination, was first fielded 50 years ago (1959) as the National Health Examination Survey. Until 1999 NHANES was fielded periodically but is now in the field continuously. Specifically, the design now allows for nationally-representative data to be publicly released every two years. The current NHANES was designed to be collected over the four-year period 2007-2010. Data collection for 2007 and 2008 has been completed. With existing resources, NCHS is maintaining sample size and content for 2009; however capital improvements for FY2009 have been reduced. Final decisions on the implementation of the 2010 survey are contingent on available resources.

For Questions Contact: Jennifer H. Madans, PhD, Associate Director for Science, National Center for Health Statistics, 3311 Toledo Road, Room 7207, Hyattsville, MD 20782, e-mail:

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Dated: February 9, 2009.

James D. Seligman,

Chief Information Officer, Centers for Disease Control and Prevention.

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[FR Doc. E9-3797 Filed 2-20-09; 8:45 am]