EMPIRICAL SIMILARITY OF RESPONSES OF 2 RANDOM SAMPLES OF NORTH-CAROLINA SWINE PRODUCERS TO A MANAGEMENT QUESTIONNAIRE USED IN THE UNITED-STATES NATIONAL SWINE SURVEY

The United States Department of Agriculture's (USDA) National Animal H ealth Monitoring System (NAHMS) National Swine Survey (NSS), implement ed in 1990, represents the first national effort to collect on-farm da ta using a statistically valid method. The purpose of the North Caroli na Swine Survey (NCSS) was to evaluate the reliability of the NSS by a ssessing the similarity of responses between the North Carolina portio n of the NSS and the NCSS using identical questions. Responses from th e North Carolina portion of the NSS (n = 40 farms) and from the NCSS ( n = 139 farms) were compared for a subset of the first three questionn aires used in the NSS. Chi-square analysis was used to test for signif icant differences between estimated proportions from the two studies. Plots of component chi-square values and frequency distribution of dif ferences between point estimates were used to evaluate the similarity between sections of the questionnaires. Approximately 75% of the 446 p oint estimates were within 15% of each other. The majority of signific ant discrepancies occurred for the biosecurity section of the second q uestionnaire, specifically for response categories of 'No' and 'N/A' ( not applicable). Percent of farms responding 'Yes' showed greater comp arability between the two studies. While most questions from the first and third questionnaires (General Swine Farm Report and the Facilitie s and Feed Report) proved to be similar, questions regarding disease p roblems, vaccination and preventive practices were less similar betwee n the two studies.