S22 = Zx22 / (r 1)
 = 0.405 / 1
 = 0.405

 Ex22 = EX22 [(ZX2)2 / r]
 = [(5.7)2 + (6.6)2] [(12.3)2 / 2]
 = 0.405



THE "MINUS" TRIAL

 This is the opposite of a "plus" trial. It compares
a technological package with alternatives that reduce the
package by one variable at a time. An example consisting
of three factors follows:


Treatment
Tech. pack. (TP)



TP variety



P nitrogen



TP plant density


Description
Tuxpefo variety; 100 kg/ha of N,
50,000 plants/ha

local variety; 100 kg/ha of N;
50,000 plants /ha

Tuxpefo variety; no nitrogen;
50,000 plants/ha

Tuxpefo variety; 100 kg/ha of N;
25,000 plants/ha


Results of the trial are shown in Table III-8.