Assessment of Performance of Commonly Used Experimental Designs (Randomized Complete Block Design, Lattice Design and Alpha-Lattice Design) in the Ethiopian Agricultural Research System
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Date
2010-10
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Addis Ababa University
Abstract
The c ho ices of experim enta l des ign as well as o f statistical ana lys is are of great importance in
fi e ld experiments. To improve production and productivity of crop yield it is important to
employ tested and proven exper imental des ign. The aim of th e study is to eva luate the prec is ion
of commonly used experimental des igns (randomi zed complete block des ign, lattice des ign and
alpha- lattice des ign) in the Ethiopian agricultural research system. Both fixed and linear mixed
effect mode ls were used to compare the effi ciency of experimental des igns. Different variety
trials co nducted at different locations by the National and Regio nal Agricultural Research
Organization in 2004/05-2008/09 years (seasons) were used in this study. The results indicate
that on average the randomized complete block design (RCBD) was more effic ient than
complete ly randomized des ign (CRD). For large miss ing va lues in RCBD, the use incomplete
block approach is more e ffi c ie nt than using miss ing-estimated approach. A Iso use 0 I' covariance
ana lys is for damaged yield in RCBD increased the re lative effic iency of RCBD compared to
CRD than the ana lys is without cova riate. The lat tice des ign was more effic ient to increase the
prec ision o f agr icultural fie ld experiments than RCBD. The re lative e ffi c iency o f a lpha latt ice
des ign compared to RCBD was 101.9% and 102.4% for both data sets respect ively. Th is
indicates that researchers ha ve in gcneral correctly co ntro lled the loca l va riability during
experimentat ion. However, the cases where blocking was not s ignifica nt can be attr ibuted to
technical issues such as orientation a nd di rection of blocking which should be improved by
researches in similar experiments. Based on the results we co nc lude that RCBD is more efficient
than CRD and lattice and a lpha lattice des igns are more effic ie nt than RCBD. In order to
increase the precision of agricultural field experiments researchers are advised to use RCBD for
small number of treatments, lattice des ign and alpha lattice desig ns for large number of
treatments.
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Keywords
Performance of Commonly Used Experimental Designs