EXPERIMENTS IN FIELD PLOT TECHNIC 35 



the coefficient of correlation and its probable error are given, for lack 

 of space. 



In the barley variety test, 1919, the effect of competition was quite 

 marked. The average yield of border rows differed from the average 

 yield of interior rows by 11.13 per cent, and the mean coefficient of 

 competition was 21.30 per cent. Attempts were made to correlate 

 competition with relative date of heading, date of maturity, grain-straw 

 ratio, and yield. The correlation coefficients determined are shown 

 in Table 10, together with the mean differences between competing 



TABLE 10. CORRELATION OF COMPETITION WITH VARIOUS CHARACTERISTICS IN 

 BARLEY VARETY TEST 1919. 



Character Mean difference be- Coefficient of correlation 



tween competing with competition 



varieties 



varieties in the characters whose relation to competition was studied. 

 Although none of these correlations is statistically significant, in 

 the strictest sense, it is noticeable that the correlation between compe- 

 tition and yield is much greater than any of the others, and is equal 

 to about four and one-half times its probable error. There was ap- 

 parently some tendency for the better yielding varieties to profit by 

 competition with the poorer yielders. On account of the relatively 

 small number of cases involved in this and the other 1919 tests, the 

 probable errors are high, and a fairly high coefficient of correlation 



TABLE 11. CORRELATION OF COMPETITION WITH VARIOUS CHARACTERISTICS IN 

 OATS VARIETY TEST 1919. 



Character Mean difference be- Coefficient of correlation 



tween competing with competition 



varieties 



may consequently fail to attain statistical significance. Such a co- 

 efficient, while not establishing the correlation, by no means indicates 

 that the correlation does not exist. 



