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Plot Plot Plot Plot Plot Plot Plot Plot

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A B A B A B A B

A systematic arrangement of plots planted to two rice varieties A and B
This scheme does not provide a valid estimate of experimental error

LESSON 3.CONTROL OF ERROR
This error is the primary basis for deciding whether an observed difference is
real or just by chance

Experimental error — refers to the differences in observations from
treatments due to environmental conditions that cannot be controlled by
the experimenter
Example: (differences in soil texture, topography, soil compaction, rainfall,
nutrient status, disease infestation, etc.).

 Any observation made within an experiment always encounter a certain
amount of error associated with it. To determine whether observed
differences in the result are due to treatments, there is a need to know
how much error was encountered within the experiment.
 Statistics allow us to quantify and assess this error (experimental
error). Several observations should be made to assess the error because
only one observation cannot estimate experimental error.
 Multiple observations associated with each treatment, or replications,
are needed.
 REPLICATE the treatments In a field experiment, BECAUSE
observations is caused by different ENVIRONMENTAL FACTORS To
ensure the estimates of experimental error for each treatment are
unbiased (not systematically influenced by underlying environmental
conditions like soil type, topography, etc.), the replications should be
randomly placed within the field.
 the two most important concepts of modern statistics are the
following:

(1) to estimate the experimental error of treatments
requires replication, and
(2) to ensure an unbiased estimate of experimental
error requires randomization of the treatments.