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Changes in Type Classifications of Dairy Cattle¹

Department of Animal Husbandry, Iowa State College, Ames

ABSTRACT

The sources of error in a subjective measurement such as type classification are comparable in kind to those to which an objective measurement is liable. However, the magnitudes of the errors from the various sources may be different. Unconscious changes in the mental ideal or scale used by the classifier correspond to imperfections in the instruments used for objective measurements. Carelessness by the classifier or his recorder is similar to incorrect placement or reading of the measuring instrument or to incorrect recording. Changes that occur in the animal's appearance, especially if the interval between classifications is long, correspond to differences in the position of an animal when it is measured at various times and are errors only in the statistical sense where the "true" measurement is that which would be approached by the average of an indefinitely large number of measurements repeated under similar circumstances.

Type classifications are only moderately repeatable.

¹ Journal Paper No. J-2826 of the Iowa Agricultural Experiment Station, Ames. Project No. 1053. This research was part of North Central Regional Project NC-2.

² Present address: Dairy Husbandry Department, Michigan State University, East Lansing.