TABLE IV-3. Analysis of variance for yield of 15
 maize varieties with four replications,
 Chimaltenango, Guatemala.

Variation d.f. SS MS Fc F.05



Blocks 3 1.109 0.3697 1.4089 N.S. 2.83
Treatments 14 8.250 0.5893 2.2458 1.94
Error 42 11.021 0.2624

Total 59 20.3800

Source: ICTA, Guatemala
CV = 11.59% N.S.: Not significant
 *: Significant at 5% level

The calculated F values (Fc) are compared with the F
values from a table to determine levels of significance.
For blocks there are 3 and 42 degrees of freedom, and for
treatments 14 and 42 degrees of freedom. The statistical
significance obtained for treatments indicates that yield
of at least one of the varieties differs from the rest.
In order to further define which varieties are
statistically different, a Tukey multiple range test for
comparison of means is performed (Steel and Torrie, 1980).
This method consists of computing a difference (D), which
would be significant at the 5% level, and comparing it
with the differences between each pair of treatment means
in the experiment. If a difference between two means is
equal to or greater than the value for D, then the two
means are significantly different.

The calculations are as follows:
 D = Q Sx where:
 Q = Value which is taken from a statistical table
 (see Steel and Torrie, 1980, pp. 588-589),
 and which is a function of number of treatments
 and degrees of freedom of the error.