74 THE MODERN MILK PROBLEM 



results would require their expression in exact statis- 

 tical correlation figures. Such have been worked out 

 from the original data and presented with inferences, 

 which corroborate and supplement the original ones, 

 by Dr. J. Arthur Harris. 6 Dr. Harris's analysis, by 

 means of the statistical figure known as the " correla- 

 tion coefficient," leads to the following conclusions: 



a. The correlation between the total scores assigned the 

 same barns by the same inspector using the three most im- 

 portant cards is only about three-quarters of its theoretical 

 maximum value. The correlation between the scores for 

 methods only is less than half its theoretical value. 



b. There is practically no correlation at all between the 

 scores assigned the barns by dairy inspectors and the bac- 

 terial content of the milk which they place upon the market. 



c. When correlations as low as those deduced from the 

 present figures are found between the bacterial counts of 

 morning and evening samples of milk from the same barns, 

 it is clear thafc much remains to be done in the perfection 

 of the technique of sampling and bacteriological analyses 

 of milk. 



These data show how flimsy is the basis for the common 

 belief that there is a relation between the score of a dairy and 

 the quality of the milk produced by it, and how premature 

 the official sanction for the grading of milk by means of dairy 



scores. 

 / 



The practical significance of such findings and earlier 

 ones of others, 7 taken in connection with the considera- 

 tions which we shall next review, is that the present 

 score cards are extremely inefficient instruments of 

 sanitation. While Mr. Brew does not construe his 

 results to disprove the value of the score card idea, he 



