Accuracy of the Estimate

This is an html transcription of the original Special Report document, authored by Rose M. Kreider, which can be found on the Census Bureau Web site in .pdf format at www.census.gov/prod/2003pubs/censr-6.pdf.

The data contained in this report are based on the sample of households who responded to the Census 2000 long form. Nationally, approximately 1 out of every 6 housing units was included in this sample. As a result, the sample estimates may differ somewhat from the 100-percent figures that would have been obtained if all housing units, and people living in group quarters had been enumerated using the same questionnaires, instructions, enumerators, and so forth. The sample estimates also differ from the values that would have been obtained from different samples of housing units, people within those housing units, and people living in group quarters. The deviation of a sample estimate from the average of all possible samples is called the sampling error.

for California

In addition to the variability that arises from the sampling procedures, both sample data and 100-percent data are subject to nonsampling error. Nonsampling error may be introduced during any of the various complex operations used to collect and process data. Such errors may include not enumerating every household or every person in the population, failing to obtain all required information from the respondents, obtaining incorrect or inconsistent information, and recording information incorrectly. In addition, errors can occur during the field review of the enumerators' work, during clerical handling of the census questionnaires, or during the electronic processing of the questionnaires.

Nonsampling error may affect the data in two ways: (1) errors that are introduced randomly will increase the variability of the data and, therefore, should be reflected in the standard errors; and (2) errors that tend to be consistent in one direction will bias both sample and 100-percent data in that direction. For example, if respondents consistently tend to under report their incomes, then the resulting estimate of households or families by income category will tend to be understated for the higher income categories and overstated for the lower income categories. Such biases are not reflected in the standard errors.

While it is impossible to completely eliminate error from an operation as large and complex as the decennial census, the Census Bureau attempts to control the sources of such error during the data collection and processing operations. The primary sources of error and the programs instituted to control error in Census 2000 are described in detail in Summary File 3 Technical Documentation under Chapter 8, "Accuracy of the Data," located at www.census.gov/prod/cen2000/doc/sf3.pdf.

All statements in this Census 2000 Special Report have undergone statistical testing and all comparisons are significant at the 90-percent confidence level, unless otherwise noted. The estimates in tables, maps, and other figures may vary from actual values due to sampling and nonsampling errors. As a result, estimates in one category may not be significantly different from estimates assigned to a different category. Further information on the accuracy of the data is located at www.census.gov/prod/cen2000/sf3.pdf. For further information on the computation and use of standard errors, contact the Decennial Statistical Studies Division at 301-763-4242.

FOR MORE INFORMATION

For more information on the children's relationship to householders in the United States, visit the U.S. Census Bureau's Internet site at www.census.gov/population/www/socdemo/ms-la.html. Data on children and on the relationship of various household members to the householder from Census 2000 Summary File 3 were released on a state-by-state basis during the summer of 2002. Census 2000 Summary File 3 data are available on the Internet via factfinder.census.gov and for purchase on CD-ROM and on DVD.

For information on confidentiality protection, nonsampling error, sampling error, and definitions, also see www.census.gov/prod/cen2000/doc/sf3.pdf or contact our Customer Services Center at 301-763-INFO (4636).

Information on other population and housing topics is presented in the Census 2000 Briefs and Census 2000 Special Reports series, locate on the U.S. Census Bureau's Web site at www.census.gov/population/www/cen2000/briefs.html. These series present information on race, Hispanic origin, age, sex, household type, housing tenure, and other social, economic, and housing characteristics.

For more information about Census 2000, including data products, call our Customer Services Center at 301-763-INFO (4636), or email webmaster@census.gov.

ACKNOWLEDGEMENT

We would like to acknowledge the assistance of Kelly Holder in the preparation and development of tables in this report.

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Credits: CENSR-6
by Rose M. Kreider

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