Investigation of Linear Type Evaluation for Collegiate Judging Contests

¹ Department of Dairy and Animal Science, The Pennsylvania State University, University Park 16802
² Department of Dairy Science, University of Florida, Gainesville 32611
³ Department of Dairy Science, University of Wisconsin, Madison 53706

Various time constraints and cow numbers were used to identify the minimum time per cow and the minimum number of cows needed to permit ranking of students for their skills in linear type evaluation. Three separate trials were conducted involving 23, 15, and 12 students from three universities who evaluated 15 traits on 30, 20, and 27 cows, respectively, using a 50-point scale. Time constraints included 1.5, 2, 3, and 4 min per cow as well as unlimited time per cow. The mean of the absolute difference between official and student scores was used to rank students. Lower means indicated greater student accuracy. Mean differences and (standard errors) across trials were 7.28 (0.24), 7.41 (0.11), 7.18 (0.11), and 7.41 (0.18) for 1.5, 2, 3, and 4 min of evaluation, respectively. The overall effect of time was not significant, and no pairs were significantly different. Rank correlations between student means suggested that 2 min of evaluation were adequate, and no advantage was found for evaluations of >3 min per cow. Rank correlations for student evaluation means based on 5 versus 10 cows were 0.85 to 0.90. Evaluation of <4 cows dropped rank correlations, but evaluation of >5 cows did not improve correlations greatly. Results suggested that use of 4 or 5 cows, evaluated at 2 to 3 min per cow, permitted accurate ranking of students for their ability to evaluate linear type traits.

Key Words: dairy cattle • linear type evaluation • collegiate judging contest

Submitted on September 18, 1995
Accepted on February 26, 1996