management practice or technological innovation generated
for the region that shows variation due to soil,
management, and/or climatic factors could be analyzed by
this procedure. Table V-3 shows a group of three trials
illustrating the combined analysis procedure. This group
of trials was evaluating the response of yield and
morphological aspects of 15 maize cultivars to prevalent
conditions in a region.
 The procedure for the combined analysis of variance
for the cultivars across the three sites was shown in
Table V-2. Each of the sums of squares (SS) was
calculated as follows:

 CF = Correction factor
 = [(Grand total of trials)2] / tbs
 = [(tot site 1 + tot site 2 + tot site 3)2]
 / (15 x 4 x 3)
 = (174.59 + 339.01 + 177.05)2 / 180
 = 2649.986

where t = number of treatments
 b = number of blocks or replications
 s = number of sites

 SSS = Sum of squares sites
 = {[(tot of observations in each site)2] / tb} CF
 = {[(Tot site 1)2 + (tot site 2)2
 + (tot site 3)2] / (15x4)} CF
 = {[(174.59)2+(339.01)2+(177.05)2] / 60}
 2649.986
 = 295.950

 SSB(S) = SS blocks (within sites)
 = [(tot observations ea/block, ea/site)2 / t]
 SSS CF
 = {[(tot block l,site 1)2 +...+ (tot block 4,
 site 3)2] / 15} SSS CF
 = {[(45.10)2 + (47.07)2 +...+ (42.42)2] / 15}
 295.968 2649.986
 = 5.2908