64 Nebraska Agricultural Exp. Station, Research Bui. 13 
The yield of the 200 individual plats varied from 56.7 to 
92.8 bushels per acre. The mean for eight groups of 25 
single plats each gives an extreme difference between single 
plats of 20.7 bushels per acre. When two, four, and eight 
systematically distributed plats are averaged, the extreme 
differences in yield are respectively 14.9, 8.9, and 7.8 bushels. 
When two, four, and eight adjacent plats are averaged, these 
extreme differences are 19, 16.7, and 15 bushels. For sys- 
tematically distributed plats the coefficients of variability for 
one, two, four, and eight plats in a group are 6.30, 4.59, 
2.91, and 2.18 per cent. For adjacent plats the coefficients 
of variabilitv for one, two, four, and eight plats in a group 
are 6.30, 5.46, 5.28, and 4.78 per cent. 
Systematic distribution of replicated plats is seen to be 
very effective in reducing experimental error due to environ- 
mental variations. 
EFFECT OF SHAPE AND SIZE OF PLAT 
The 207 thirtieth-acre Kherson oats plats described in 
the preceding discussion were grouped to enable a compari- 
Various ways of combining plats to make plats of 
different sizes and shapes (Table 31) 
