Experimental Error in Crop Tests 
61 
REDUCTIOX OF ERROR BY REPLICATIOX 
Tha actual yields from the first 200 of these similarly 
treated plats of Kherson oats, described on pages 52 to 60, 
have been compiled to show the extreme variations, average 
and standard deviations from the mean, and the coefficients 
of variability for single plats and for the mean yields of two, 
four, and eight piats averaged together. These groupings 
have been arranged for both adjacent and systematically dis- 
tributed plats. The results are given in Table 31. 
It is clearly shown that replication greatly reduces the 
extreme variation and coefficient of variability in the yield 
of field plats. A given number of replications are also much 
more effective when systematically distributed than when 
adjacent plats are averaged. 
Fig. 15 — Harvesting thirtieth-acre plats of Kherson oats. The binder 
has a gasoline engine attached which cuts and binds the grain. This 
facilitates cleaning out the binder quickly at the end of each plat. 
Note the narrow bare spaces between plats. If the plats are tangled 
by lodging, they are separated by hand before being cut. This 
shape of plat is very convenient, since it is one drill in width and 
may be harvested by one swath of the binder 
