For treatments: F = MST / MS(SxT)
 = 2.952 / 1.021
 = 2.89**

For site-by-treatment interaction: F = MS(SxT) / MSE
 = 1.021 / 0.394
 = 2.59

All of these F values are highly significant (P<0.01).

TABLE V-4 Combined analysis of variance for yield of the
 maize varieties evaluated in three sites,
 Chimaltenango, Guatemala.

Sources of d.f. SS MS Fc F.01
variation

-Sites (s-l)=2 295.950 147.975 144.93 7.64
-Blocks s(b-1)=9 5.2908 0.588
(within
sites)
-Trts. (t-1)=14 41.3328 2.952 2.89 2.80
-Sites x (s-l)(t-1)=28 28.5818 1.021 2.59 1.87
trts.
-Error s(b-1)(t-1)=126 49.5936 0.394
-Total (sbt)-1=179 421.049

Source: ICTA
CV = 16.4%

 The treatment means for each site and overall
treatment means are presented in Table V-5. As one
studies this table, the reason for the very highly
significant effect of sites becomes obvious. The mean
yields for the cultivars in Site 2 (Parramos) are, in most
cases, nearly double those of the other sites, so this
site is responsible for the highly significant difference
among sites. The effect of the site-by-treatment
interaction is evident when studying individual cultivars.
As an example, cultivar 2 has a high yield in Site 3 and
a low yield in Site 2. Cultivar 13 responds the opposite
way. See Chapter VII for a means of further analyzing
this interaction.