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 EXAMPLE: ANIMAL FEEDING TRIAL
 Initial weight of the animals differ. This initial
weight will be used as the covariate. , Final weight
of the animals after they are subjected to various
feeds could be adjusted to values that could have
been attained had all animals started with the
same body weight.
 Or in a field experiment where some experimental
plots were damaged by rats., covariance analysis
with rat damage as the covariate can adjust plot
yields to levels that they should have been with no
rat damage in any plot

Lesson 4. STATISTICAL INTERPRETATION AND ANALYSIS OF RESULTS
PROPER INTERPRETATION OF RESULTS

 An important feature of the design of experiments is -----the ability
to maintain uniformly all environmental factors that are not part of
the treatments being evaluated.
 Maintaining uniformity is vital to measurement and reduction of
experimental error which is important in hypothesis testing.
 In field experiment like rice the choice of management practices:
weed control, fertilization, site and crop season (rainy, dry) will
greatly affect the performance OF Variety A and B.
 It is a fact that new varieties perform better than native varieties
when grown in a good environment and good management: but
improved varieties are poorer when grown with native using
traditional methods.
 Thus Result of Experiments is applicable only to conditions that
are similar but this is troublesome since most experiments are
done in experiment stations where average productivity is higher
than that for ordinary farms.

 Crop experiments should be conducted for several crop seasons,
and years in farmer’s fields and research stations to insure that
results will apply over a wide range of environments.

STATISTICAL SIGNIFICANCE?

When a researcher presents a TERMINAL REPORT OF HIS RESEARCH
STUDY or thesis he usually make reference to “statistical significance” or
a variant that contributes to statistical analysis and its use in determining
treatment differences.