الفهرس 
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Abstract
SUMMARY AND CONCLUSION
Relative precision, i.e., relative efficiency of
different experimental designs has been investigated by
many researchers.
In Egypt results from uniformity trials with different
field crops have been reported by several investigators,
such as, El-Kadi. (1973). El-Rassas (1982) and Moursi et ale
e 1983) .
In cotton, several trials have also been ~onducted.
However, some major points have not as yet being
calculated such as the efficiency of covariance ~nalysis,
regression analysis arid guarded hills procedure.; Thus,
thiS work has been conducted with the objective of evaluating
the relative efficiency of different experimental.
designs and techniques in experimental field work of cotton .
. ..Two.~fleld”expe[’imental tr.ials. were_conducted. a
uniformity trial in 1982 and the second was designed in
randomized complete block design with six replications in
1983. In the first trial of 1982. Giza 75 the cotton
cultivar was used. The second trial of 1983 included in
addition to Giza 75. the cotton cultivars Giza 69, Giza 70
and Giza 45, Data collected included seedcotton yield and
some major components of yield. These were utilized in
computing relative efficiency estimates. Results are
summarized as follows:
5.1. The relative efficiency of experi~ental designs:
The randomized complete block design was more efficient
than the completely randomized design (106.47%).
- The latin square design was more efficient than the
randomized complete block (110.45%). Also, the relative
efficiency of rows was higher than that of columns.
- The split-plot, split-split-p1ot and strip plot designs
were of higher efficiency as to their sensitivity to
measure interaction (115.38, 131.79 and 143.40% for splitplot,
split-split-plot and strip-p16t designs, respectively).
- The incomplete block designs were more efficient than the .’
randomized complete block design (126.20%).
- The balanced incomplete blocks were more efficient than
the partially balanced designs (133.88% and 141.91% for
balanced and partially balanced, respectively).
- The double control procedure warranted a higher degree of
efficiency than single control (123.97% and 113.25% for
double control and single control, respectively).
- The” square- lattices expressed h~igher-e’fficiency than-the
rectangular lattices (132.22% and 97.60% for square
lattices and rectangular lattices, respectively).
- The Lat t tce square designs were more efficient than the
rectangular lattices.
5.2. The relative efficiency of plot and block size and
shape:
- The rectangular large plots were of higher efficiency
(140.34%), especially when the length of plots runs in
parallel to the direction of soil heterogeneity in
experimental units.
An inverse relationships between both plot sizes and
number of treatments and coefficient of variability was
observed.
- There is no clear difference in efficiency of square
blocks or rectangular blocks.
5.3. The relative efficiency of covariance analysis and
guarded hills procedures:
_ Covariance analysis (ANCDVA) was found more erficient
than the analysis of variance (ANOVA) for adjusted treatment
means.
- The guarded plants procedure was more efficient’than its
counterpart of unguarded plants.
5.4. The relative efficiency of multiple linear regression:
- Model II was found more efficient than Model I. This may
be attributed to the fact that the number of bolls per
branch is more essential in determining seedcotton yield
than the length of fruiting branch per plant.
- Other components were of similar weight in both models.
- All genotypes tested gave the same trend in both seasons
by using the two models. This indicates that the importance
of yield components variables fitted in the model
also, do not change in relation to seasonsl variations.
On the other hand, there is no effect of the seasonal
variations on different studied characters of yield
components.
In comment, the findings reported herein coincide with
the moderntheo ry of expe rimen tal design that calls for
randomization, local control and central of experimental
error with a minor deviation, i.e. results on randomization
vs. systematic distribution of treatments wereir~es~lute.
This, however will not underestimate ~he importance of
randomization in experimental design because randOUiization
is necessary to destroy the correlation among errors and
make valid the usual tests of significance. Also, the
importance of block shape on precision was not ·clear.
Various uniformity trial studies, with different field
crops have shown that the block whether complete or .
incomplete should be apprOXimately square. The findings
of this work agree with thos~ previously reported by
others. In addition to that, the importance of guarded
hills procedure was made clear. No advantage of guarded
hills over unguarded hills procedure was observed. The
reason given was that ~he relationship of number of plants
on a given area and seedcotton yield per plant is compensatory
in its nature. However, data reported herein showed
undoubtdly the importance of guarded hills procedure.