of sampling error is, relatively speaking, not an appropriate criterion for judging the quality of the census. Although block counts may contribute to the congressional redistricting process, for example, it is important to keep in mind that the results in a redistricting process are the counts for the congressional districts that are eventually created (and to a lesser extent, the counts for districts that were, or conceptually might have been, considered but were discarded). For these kinds of counts, the level of sampling error will be modest because the larger the number of observations used for an estimate, the smaller its sampling error will be.

Thus, in the panel's view, the important considerations for evaluating whether the amount of sampling error present in the census process is acceptable are not those that relate to counts for very small units, such as blocks. It is clear that at that level, sampling error may be substantial in some cases (again, relative to the size of the block). The evaluation of sampling error should take place for the geographic level counts that have important legal, political, or financial implications. For such levels, a census that uses sampling can achieve results that are at least as good as those from a more time-consuming and expensive effort to obtain a completed form for every household.

In summary, then, as we have stated before, the panel concludes that the use of sampling and statistical estimation are important components of the plans for the 2000 census. Both sampling for nonresponse follow-up and sampling for integrated coverage measurement are key to the successful conduct of an affordable enumeration of adequate quality in all parts of the country. Although each type of sampling improves both efficiency and quality, sampling for nonresponse follow-up will make the greatest contribution to cost savings, while integrated coverage measurement contributes more to improved accuracy. The Census Bureau needs to carry out further research to develop the specific details of how each of these components is to be conducted and how they are to be integrated. The Census Bureau must also be careful to inform knowledgeable users of the methods to be used and the reliability of the counts that will be obtained.

If sound procedures are developed by the Census Bureau and communicated to users, the panel believes that it will be possible for the Bureau to address all reasonable potential objections to the use of sampling and to satisfy users that the use of sampling has added to the soundness and quality of the 2000 census, rather than detracting from it.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement