. Proceedings of the American Society of Agronomy . ts. Inthe most carefully conducted experiments check plats or those havingsimilar treatments have occurred every third plat. It seems possible that the use of smaller plats on which the sametreatment is repeated several times, the replicate plats being locatedon different parts of the field, may have some advantages over usingthe larger plats. Plats of this kind have been laid out on the experiment field atCornell University and comparisons may be made with tenth-acre LYON : EXPERIMENTS TO ESTIMATE ERRORS. 93 plats in the same field. The smal
. Proceedings of the American Society of Agronomy . ts. Inthe most carefully conducted experiments check plats or those havingsimilar treatments have occurred every third plat. It seems possible that the use of smaller plats on which the sametreatment is repeated several times, the replicate plats being locatedon different parts of the field, may have some advantages over usingthe larger plats. Plats of this kind have been laid out on the experiment field atCornell University and comparisons may be made with tenth-acre LYON : EXPERIMENTS TO ESTIMATE ERRORS. 93 plats in the same field. The small plats are one hundredth acre insize, being feet long and 10 feet wide. They are separated bya two-foot space. When planted to small grain this intervening spacecontains two rows of grain which are removed before harvest. Whenplanted to maize one row occupies the two-foot space and this row isremoved before harvest. An evident advantage in the small plat isthe greater care that can be given the experiments without increasinggreatly the 160-70 170-80 180-90 I90:i00 200(0 ^30 Fig. 2.—Frequency curve; yield of maize on plat 1201-1237. In 1911 a series of these plats was planted to maize in order totest the uniformity of the land. All of plats 1,201-1,237 were giventhe same soil treatmient. The yields of silage on these plats whenplotted in a frequency curve are shown in Fig. 2. The curve is suffi-ciently uniform to justify the use of the figures for calculating theprobable error which may be expected to occur on any plat in theseries in this particular test. The crop of another year may give adifferent result, but a repetition of the test for a number of yearsshould allow an approximately accurate conclusion as to the probableerror which may be expected. For the calculation of probable error the formula = ^|~ 94 PROCEEDINGS OF THE AMERICAN SOCIETY OF AGRONOMY. has been used, in which 6^ equals the sum of the squares of the per-centage deviation
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