1909.] The Experimental Error in Field Trials. 367 



method, we shall find that the ''probable error" of the mean 

 result is about 2 per cent.; i.e., from the fifty years' results 

 we may conclude that there is an inherent superiority in 



Table I. — Actual and Relative Yield on Two Unmanured 



Grass Plots, Rothamsted. 





Yield 0 



f Hay. 



Relative 





Yield of Hav. 



Relative 







yield of 









yield of 









Plot 12. 









Plot 12. 

















Plot 2 



Plot 12. 



Plot 3 

 = 100. 





Pint 2 

 r 101 j,. 



Plot 12. 



Plot 3 

 = 100. 





lb. 



lb. 







Id. 



IK 



lb. 







2 ,5 r 5 



2,35 J 



93 



1552 



2,524 



2,340 



93 





2,050 



2,592 

 3,3 6 ° 



91 



I003 



2,2o0 



2,322 



102 



.0.0 

 1350 



2,472 



T "if*. 

 130 



1 554 



I ,504 



1,996 



111 



1559 



2,540 



2,576 



IOI 



1555 



2, IOI 



2,339 



1 1 1 



I50O 



2,760 



2,554 



104 



1 000 



2,547 



2,672 



1Q 5 



1501 



O 8 A A 

 2,544 



3,3°4 



I IO 



1 557 



1 >47;i 



L33° 

 2,298 



90 



I502 



3,°5 2 



3,4 2 4 



112 



1 000 



2,296 



100 



1803 



2,284 



**> Si A A 

 2,544 



I2 5 



1559 



2,638 



2,383 



9° 



IOO4 



0 ACQ 

 2,055 



2,505 



104 



T QaA 

 I590 



1,648 



i,565 



95 



1565 



1,290 



L93 2 



149 



I 59 I 



2j06o 



2, 422 



T T G 

 115 



1866 



2,66o 



3,CI2 



113 



1892 



1,627 



2^130 

 487 



131 



1867 



2 221 



2 oa8 



Q I 



i8cn 



391 





1868 



1,960 



2,676 



137 



1894 



2,685 



2,538 



95 



1869 



4,256 



4,352 



I02 



1895 



1,402 



L399 



100 



1870 



644 



1,260 



196 



1896 



1,144 



1,272 



1 1 1 



1871 



2,844 



2,960 



IO4 



1897 



1,742 



2,048 



118 



1872 



1,644 



2,252 



137 



1898 



1,922 



2,256 



117 



1873 



1,372 



1 304 



131 



1899 



1,342 



1,788 

 1,859 



133 



1874 



1,412 



1,642 



Il6 



1900 



*, 379 



135 



1875 



3,620 



4,232 



117 



1901 



455 



765 



168 



1876 



1,384 



1,599 



Il6 



1902 



1,004 



1,200 



119 



1877 



2,3 6 4 



2,165 



92 



1903 



L509 



i,57i 

 2,872 



104 



1878 



1,848 

 3,028 



1,832 



99 



1904 



2,949 



97 



1879 



3,LS7 



• 104 



I905 



L93 6 



2,297 



119 



1880 





1,081 



127 











848 











1881 



1,480 



1,393 



94 



Average 



2,057 



2,254 



1 10 



Table II. 



Plot. 



1904. 



Swedes. 



1905. 



Barley. 



1906. 

 Mangolds. 



1907. 

 Wheat. 



1908. 



Swedes. 



Mean of 

 5 years. 



A 



98-1 



88-8 



95-8 



86-3 



92-8 



92-3 



B 



95-8 



92-4 



90-6 



95*1 



94 '9 



937^ 



C 



IOIO 



98-9 



99-2 



I02'4 



IOO"2 



100-3 



D 



101 7 



114-1 



105-0 



109- 1 



114-9 



109-0 



E 



103-4. 



105-8 



109-2 



107-0 



97'3 



104-5 



Plot 12 over Plot 3 which is certainly more than 8 but less 

 than 12 per cent. The mean error of a single year's result is, 

 similarly, 10 per cent. 



Taking another example, Table II. gives the results ob- 

 tained in the last five years on five plots in Little Hoos Field 



