The 1987 Census of Agriculture Coverage Evaluation 

 used the area segment sample of the 1 987 June Enumer- 

 ative Survey (JES) of the National Agricultural Statistical 

 Service (NASS) to estimate farms not on the census mail 

 list. The Census Bureau contracted with the NASS to 

 augment the JES data collection and receive survey data 

 under the confidentiality protection afforded by Title 13, 

 U.S. Code, from all residents of area sample segments 

 with agricultural activity. These survey records were matched 

 to the census mail list. Records that did not match were 

 mailed a census of agriculture report form to estimate mail 

 list coverage. Estimates of farms not on the census mail 

 list used the capture-recapture dual frame estimator that 

 will be described in the Coverage Evaluation report. 



Table F provides coverage evaluation estimates of the 

 number of farms not on the mail list and selected charac- 

 teristics of those farms with their percent relative standard 

 error. The table also provides an estimate of characteris- 

 tics of farms not on the mail list as a percentage of total 

 farms in the United States. The estimate of total farms in 

 the United States is based on census farm count and the 

 estimated number of farms not on the census mail list. This 

 estimate of total farms in the United States was not 

 adjusted for classification and list duplication errors. Esti- 

 mates of these errors will be available in the Coverage 

 Evaluation report at the regional and U.S. levels. The table 

 provides the standard error (not relative standard error) of 

 this percent estimate. 



Respondent and Enumerator Error 



Incorrect or incomplete responses to the mailed census 

 report form or to the questions posed by a telephone 

 enumerator introduce error into the census data. Such 

 incorrect information can lead, in some cases, to incorrect 

 enumeration of farms. This type of reporting error is 

 measured by the Classification Error Study discussed later 

 in this section. To reduce all types of reporting error, 

 questions were phrased as clearly as possible based on 

 tests of the census report form, and detailed instructions 

 for completing the report form were provided to each 

 addressee. In addition, each respondent's answers were 

 checked for completeness and consistency. 



Item Nonresponse 



Nonresponse to particular questions on the census 

 report that we would logically or statistically expect to be 

 present may create a type of nonsampling error in both 

 complete count and sample data. When information reported 

 for another farm with similar characteristics is used to edit 

 or impute for item nonresponse, the data may be biased 

 because the characteristics of the nonrespondents have 

 not been observed and may differ from those reported by 

 respondents. Any attempt to correct the data for nonre- 

 sponse may not completely reflect this difference either at 

 the element level (individual farm operation) or on the 

 average. 



Processing Error 



The many steps of processing of each census report 

 form are sources for the introduction of nonsampling error. 

 The processing of the census report forms includes cleri- 

 cal screening for farm activity, computerized check-in of 

 report forms and followup of nonrespondents, keying and 

 transmittal of completed report forms, computerized edit- 

 ing of inconsistent and missing data, review and correction 

 of individual records referred from the computer edit, 

 review and correction of tabulated data, and electronic 

 data processing. These operations undergo a number of 

 quality control checks to ensure as accurate an application 

 as possible, yet some errors are not detected and cor- 

 rected. 



Classification Error 



An evaluation study of classification errors was con- 

 ducted in the 1987 Census of Agriculture as part of the 

 census coverage evaluation program. A sample of mail list 

 respondents was selected, and these addresses reenu- 

 merated to determine whether they were a farm or non- 

 farm. A farm status determination was made based on the 

 evaluation questionnaire and compared with the status 

 based on the data reported on the census form. Differ- 

 ences in status were reconciled. 



In past censuses, the proportion of farms undercounted 

 due to classification errors was higher for farms with small 

 values of sales. The classification error rate was higher for 

 (1) livestock farms than crop farms, (2) farms with a small 

 number of acres than larger farms, or (3) tenant farms than 

 full or part-owner farms. Results from the 1 987 classifica- 

 tion error study will be published in the Coverage Evalua- 

 tion report. 



EDITING DATA AND IMPUTATION FOR ITEM 

 NONRESPONSE 



For the 1987 Census of Agriculture, as in previous 

 censuses, all reported data were keyed and then edited by 

 computer. The edits were used to determine whether the 

 reports met the minimum criteria to be counted as farms in 

 the census. Computer edits also performed a series of 

 complex, logical checks of consistency and completeness 

 of item responses. They provided the basis for deciding to 

 accept, impute (supply), delete, or alter the reported value 

 for each data record item. 



Whenever possible, edit imputations, deletions, and 

 changes were based on component or related data on the 

 respondent's report form. For some items, such as oper- 

 ator characteristics, data from the previous census were 

 used when available. Values for other missing or unaccept- 

 able reported data items were calculated based on reported 

 quantities and known price parameters. 



1987 CENSUS OF AGRICULTURE 



APPENDIX C C-5 



