Methods of making determinations and interpreting results in grain grading

Unequal division of the original sample by some Boerner samplers does not affect the grade of the grain unequally divided. Taking samples for multiple determinations from different halves or fourths of the original sample has no advantage as far as accuracy is concerned over taking contiguous samples of the same size or one sample of the same size as the total of the smaller ones. The indications are that samples for percentage determinations of 100 grams in size give significantly greater accuracy than samples of smaller size. Further reduction of variability of determinations may be secured in approximately one-half of the cases by the use of samples 200 grams in size, but on account of the labor necessary in making separations on this size of sample it cannot be considered for use except for corn and in exceptional cases in making foreign material determinations on oats. Even with the utmost care in making determinations on single or duplicate samples of the largest practical size, variability still occurs and the element of chance enters to a considerable extent into the grading of lots of grain which come near the grade limits. To eliminate chance as far as possible in the grading of grain, a system of tolerances is proposed for heat damage and foreign material, based on the variability secured from determinations on a considerable number of samples of various weights taken from wheat containing approximately the grade limits of damage or of foreign material other than cereal grains. Tolerance percentages of 30%, 20%, 10%, 10% and 5% below the present grade limits are suggested, respectively, for heat damage determinations in wheat containing approximately 0.1%, 0.2%, 0.5%, 1.0% and 3.0% of this kind of damage when samples 100 grams in size are employed. When 50 gram samples are used tolerances of 35% for wheat containing 0.1% heat damage and 25%, 15%, 10% and 5% below the present grade limits respectively for wheat containing 0.2, 0.5, 1.0 and 3.0% are indicated. The use of tolerance percentages such as the ones suggested justifies the placing of lots of wheat samples which vary below the grade limit by the amount of the tolerance in the grade above. This should result in more equitable grading than is possible where no tolerance is used in connection with the grading of wheat near the grade limits. The use of the tolerance percentages suggested does not have the same effect as lowering the grade limits since there would be variability on either side of any new grade limits established necessitating still the use of tolerance percentages to promote more equitable grading.