No. 527] SHORTER ARTICLES AND DISCUSSION 



097 



TABLE III 



S<nuj)ii)uuia Ctnimh »sis. Table TIT gives 1 lie frequency and the 

 total numbers of ovules produced for each length-class. 



S(x'y') =1,217,367." 

 We now calculate the correlation for the length and ovules per 

 placenta or length and total ovules at pleasure. In the first class 



r= (1,317,367/2000) 39.70:?- 14.952 

 r ~~ 6.30704 < 4.61361 ' ~ " 



and in the second 



_ (1,217,367/1000) — 39.703 X 29.904 _ 



Again, a worker may have the means and variabilities for two 

 characters p and q, and wish to obtain the correlation without 

 trouble of preparing a formal table. He simply seriates his cards 

 according to the p character, sums the values of the associated q 

 characters and writes down grades of p and the associated totals 

 in a table like II or III. The remainder of the work is as illus- 

 trated above. 



Or, finally, in short series r may be very quickly calculated by 

 summing the product of the values of the two characters of the 

 individuals, dividing by the total number, subtracting the prod- 

 uct of the two means, and dividing the result by the product of 

 the two standard deviations. 



