Statistical modelling
From the output for the first 30 day-period it can be seen that the residual mean square is 1376 g2 with 13 degrees of freedom. The covariate pre_milk_yld is highly significant and has been very effective in reducing the residual variance for average yield during the experiment (from 7476 g2, which can be shown to be the residual mean square by re-running GenStat without a covariate term in the model). The analysis of covariance shows that the different feeding patterns had no significant effect on milk yield. Goats receiving diet A had the highest mean milk yield (240.3 g) compared to those on diets B and C (196.7 and 197.9 g, respectively).
Analysis of variance (adjusted for covariate)
Source
|
d.f.
|
s.s.
|
m.s.
|
v.r.
|
F pr.
|
Batch stratum
|
Covariate
|
1
|
55822
|
55822
|
|
|
Batch.*Units* stratum
|
Diet30
|
2
|
7281
|
3641
|
2.65
|
0.109
|
Covariate
|
1
|
86778
|
86778
|
63.08
|
<.001
|
Residual
|
13
|
17884
|
1376
|
5.43
|
|
Total
|
17
|
180276
|
|
|
|
|
|
|
|
|
|
Grand mean
|
211.6
|
|
|
|
|
Diet30
|
C
|
A
|
B
|
|
|
|
197.9
|
240.3
|
196.7
|
|
|
rep.
|
6
|
|
|
|
|
d.f.
|
13
|
|
|
|
|
s.e.d.
|
21.82
|
|
|
|
|
|