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CBECS Home Page 2. Nonsampling and Sampling Errors:
1995 Detailed Tables |
2. Nonsampling and Sampling Errors
Introduction All of the statistics published in this report are estimates of population values, such as the total floorspace of commercial buildings in the United States. These estimates are based on reported data from representatives of a randomly chosen subset of the entire population of commercial buildings. As a result, the estimates always differ from the true population values. The differences between the estimated values and the actual population values are due to two types of errors, sampling errors and nonsampling errors. Sampling errors are errors that are random differences between the survey estimate and the population value that occur because the survey estimate is calculated from a randomly chosen subset of the entire population. The sampling error, averaged over all possible samples, would be zero, but since there is only one sample for the 1995 CBECS, the sampling error is nonzero and unknown for the particular sample chosen. However, the sample design permits sampling errors to be estimated. “Estimation of Standard Errors” describes how the sampling error is estimated and presented for statistics given in CBECS detailed tables and reports.The next two sections, “Data Collection Problems” and “Nonresponse,” describe some of the sources of nonsampling error in the Building Characteristics Survey and how that portion of the CBECS is designed and conducted to minimize such errors. Nonsampling errors can result from (1) inaccuracy in data collection due to questionnaire design errors, interviewer error, respondent misunderstanding, and data processing errors; (2) nonresponse for an entire sampled building (unit nonresponse); and (3) nonresponse on a particular question from a responding building (item nonresponse). The section “Data Collection Problems” addresses some of the difficulties encountered in trying to obtain meaningful energy data on questionnaire items in the 1995 survey. The section “Nonresponse” presents survey design and data collection procedures used to minimize unit and item nonresponse in both the Building Characteristics Survey and the Energy Suppliers Survey. The energy consumption and expenditures data were based on monthly billing records submitted by the buildings’ energy suppliers. The section “Annual Consumption and Expenditures” provides a detailed explanation of the procedures used to obtain annual consumption and expenditure estimates from the bills, as well as the procedures used to handle partial or completely missing data. The peak electricity demand estimates were also based on the monthly billing data, as described in the section “Annual Peak Electricity Demand.” The section titled “Other Problems” discusses reconciliation of building and supplier reports on the types of energy sources use; and attempts to collect natural gas expenditures from both the local natural gas suppliers and non-local natural gas suppliers. Top Continue to “Data Collection Problems” Specific questions on these topics may be directed to: Joelle Michaels joelle.michaels@eia.doe.gov CBECS Manager Phone: (202) 586-8952 FAX: (202) 586-0018 URL: http://www.eia.doe.gov/cbecs/tech_errors_intro.html |