178 MAINE AGRICULTURAL EXPERIMENT STATION. I9I4. 



In the long run the most desirable variety is that one which 

 will give a high yield under any of the conditions that are likely 

 to be met with in any season. A variety which yields very 

 highly in a favorable season may not be so desirable as one 

 which yields moderately well every year regardless of the sea- 

 son. The standard deviation and the coefficient of variation 

 as given in Table 8 measure the amount of variation in the yield 

 of a given variety for the four years. We have already dis- 

 cussed the variation in the 191 3 plots in connection with Table 

 7. In any one year all the plots are subjected to the same sea- 

 sonal conditions. When the yields of several seasons are com- 

 pared we are taking account of the effect of differences in the 

 seasons as well as of differences in the soil. It will be of inter- 

 est to compare the variation of the plots in a single season with 

 the variation during several years. For this purpose we may 

 compare the two coefficients of variation for the eleven varie- 

 ties discussed above. These constants have been brought to- 

 gether in Table 9. The varieties are arranged in this table in 

 the order of their variation coefficients for the yield of the four 

 years. 



Table 9. 



Comparison of the Variation in Yield of the Plots in Four 

 Different Years with the Plots in a Single Year. 



Variety. 



Coefficient of 

 Variation for 



4 years 

 production. 



Coefficient of 



Variation for 



the 1913 plots. 



Difference. 





3.61 ±0.86 



4 . 49 ± 1 . 07 



8.85±2.13 



9.02 ±2.17 



11.30 ±2.73 



12.23±2.96 



12.94 ±3.14 



14.19±3.45 



14.51 ±3.53 



15.05 ±3.67 



19.43 ±4.81 



11.42±2.76 

 3.54 ±0.85 

 5.42±1.30 

 7.96±1.91 

 9.66±2.09 

 6.55±1.57 



24.51 ±6.19 

 4.97±1.20 

 6.23±1.49 



12.41 ±3.00 

 8.80±2.11 



-7.81 ±2.89 





+0.95±1.37 





+3.43 ±2.50 



Prosperity 



President 



Silver Mine 



Senator 



+1.06 ±2.89 

 +1.64 ±3.44 

 +5.68 ±3.35 

 -11.57 ±6.94 

 +9.22 ±3.65 





+8.28 ±3.83 



Banner _ 



+2.64 ±4.74 

 +10.63 ±5.22 







Average 



11.42 



9.32 



+2.20 



From this table we may first discuss the variation coefficients 

 for the yield of the four years as given in the second column. 

 It will be noted : 



