Sample Design

The data contained in the STP2 are based on the Census 2000 sample, and are estimates of the actual figures that would have been obtained from a complete count. These estimates are subject to both sampling and nonsampling error.

Every person and housing unit in the United States was asked basic demographic and housing questions. A sample of these people and housing units was asked more detailed questions about items such as income, occupation, and housing costs. The sampling unit for Census 2000 was the housing unit, including all occupants. There were four different housing unit sampling rates: 1 in 8, 1 in 6, 1 in 4, and 1 in 2, for an overall average rate of about 1 in 6. To calculate the standard errors for STP2 data, the following were used: the unadjusted standard error for the characteristic that would result under a simple random sample design; the design factor for the characteristic estimated based on the sample design and estimation techniques employed to produce Census long form data estimates; the number of people, housing units, household, or families in the publication area; and the observed sampling rate. For more information about the sample design of the STP2, please refer to the following URL: http://nces.ed.gov/surveys/sdds/ref00.asp. This URL provides detailed information on calculating standard errors for estimates in this report derived from the STP2. To view the standard errors for the STP2 estimates in this report, see appendixes E, F, and G.