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MISSOURI AGR. EXP. STA. RESEARCH BULLETIN 49 



ductivity of the same portion of the field as determined by an adjacent 

 Red Rustproof check plot. This correlation is shown in figure 7. The 

 coefficient of correlation is less than three times its probable error 

 the correlation has not even statistical significance ! The relative pro- 

 ductivity of different portions of the field, as indicated by the two check 

 varieties, is shown in figure 8. If Kherson had been used as a check 



FIGURE 8. RELATIVE VARIABILITY OF DIFFERENT PARTS OF AN EXPERIMENT 

 FIELD, AS INDICATED BY THE YlELDS 0* ADJACENT CHECK PLOTS OF KHERSON 

 AND RED RUSTPROOF OATS. OATS VARIETY AND STRAIN TESTS 1921. In the 

 diagram on the left, points of equal productivity, as indicated by the yields 

 of the Kherson check plots, are connected by lines (as points of equal elevation 

 are connected by lines on a contour map). In the diagram on the right, the 

 same field is similarly mapped according to the yields of the Red Rustproof 

 check plots. The numbers indicate the plot values of the points concerned. 



variety for adjusting yields, the yields of certain plots would have been 

 increased to compensate for the low productivity of the soil; if Red 

 Rustproof had been used the yields of the same plots would have 

 been decreased to compensate for the high productivity of the same 

 soil. The fact is that certain parts of the field were actually more 

 productive than the average for Kherson oats and less productive for 

 Red Rustproof, as is indicated by the fact that each variety of check 

 was considerably more effective in the adjustment of the yields of 

 strains of the same variety than of strains of the other. But neither 

 check was a very accurate measure of the productivity of the soil, 

 even for its own variety, as indicated by the failure of adjustment to 

 reduce variability consistently even when Kherson strains were ad- 



