Dec. i, 1920 Permanence of Differences in Experimental Plots 337 



A. — PUBLISHED DATA 



Unfortunately few data are available for analysis from the literature. 

 Lehmann has given (4, p. 6) yields of paddy on the 17 plots of ranges 

 B and C, respectively, of the wet tract of the Experimental Farm at 

 Hebbel. Grouping the yields for the two ranges, we find for the corre- 

 lations between the yields of the same plots in the two years 1905 and 

 1906: 



Range B, r = 0.834 ±0.050, r/Er= 16.7. 

 Range C, f = 0.799 ±0.059, r/Er= 13.5. 



Stockberger (7) gives data for the extremes of a series of hill yields 

 for hops. The interannual correlations deduced from these data have 

 been shown (2) to be as follows: 



Vwrs Lowest Highest 



hills. 



1909 and 1910 " o. 29±o. 17 o. 59±o. 13 



i9ioandi 9 n 55 ± . I3 . $2 ± . I4 



1909 and 1911 43 ± .15 . 30± . jg 



Stockberger has also given (8) the yields for 30 rows, each 210 feet" 

 in length, from hop fields of several hundreds of acres in the Sacramento 

 Valley of California : 



The plants in these rows averaged well in number and uniformity of growth with 

 the plants on several hundreds of acres of hops in the midst of which the experimental 

 area was located . • 



Data are available for the years 1909 to 1914. Calculating the corre- 

 lation between the yields in the different years, we have the results 

 set forth in Table I. It appears that with one single exception the con- 

 stants are positive throughout. In general they are significant in com- 

 parison with their probable errors, indicating a superiority in a subsequent 

 year if. a superiority is shown in a given year. 



The constants in the table are arranged in a way to show the change 

 in the coefficient of correlation as the years become more widely separated 

 in time. Thus, in the case of the correlation for the 1909 yields, the 

 constant for "first and second" is that showing the relationship between 

 the 1909 and 1910 yields, while "first and third" indicates the constant 

 measuring the relationship between the yields of 1909 and 191 1. Simi- 

 larly, in the series of coefficients for 1910 "first and second" designates 

 the correlation between 1910 and 191 1, etc. 



For the series beginning with 1909 we note a marked decrease in the 

 magnitude of the constants as the yields correlated become more widely 

 separated in time. The same is true for the series beginning with 1910. 

 The other series are more irregular. 



