Hayes and Garber - Cucurbit Breeding

FIELD PLOT TECHNIC 57
error and, therefore, under the assumed conditions of the experiment,
of little significance, as is indicated by Table X taken from
Pearl and Miner (1914).
Use of Probable Error in Eliminating Strains. The probable
error obtained by means of the checks may also aid in selecting
an elimination value below which varieties or strains may be discarded
without danger of throwing away a valuable one.
This
figure is necessarily more or less arbitrary and will depend upon
the desired degree of accuracy. The magnitude of the figure
which is multiplied by the probable error will also depend somewhat
upon the desired amount of elimination. The method
used at the Minnesota Station is to subtract the product of three
times the probable error for the method of test multiplied by
\/2 from the highest or one of the higher yielding strains. The
difference gives a figure below which it is considered safe to discard
without danger of eliminating a high yielding strain. If
the yield of a strain falls below the elimination figure for two or
three years, it is discarded from further trials.
The Pairing Method of Securing a Probable Error. Under
certain conditions it is impracticable to devote so large a share
of the experimental field to check plots. Wood and Stratton
(1911) have suggested a means of securing a reliable probable
error without the aid of checks. Briefly, their method consists
of systematically pairing similarly treated plots and finding their
mean yields. The deviation of this mean from the yield of the
Plot
original plots is expressed in percentage of the mean. The following
illustrates the procedure:
arrange-