14 BULLETIN 1300, U. S. DEPARTMENT OF AGRICULTURE 
nation by yield, 12 per cent by acreage, and 10 per cent joint de- 
termination, due to the correlation of +0.19 between yield and 
acreage. These coefficients of determination amount to 86 per cent. 
The remaining 14 per cent must, of course, be spurious and due to 
such conditions as the combination of the factors by multiplication 
instead of addition, lack of linearity in the regressions, and incon- 
sistencies in the fitting of the trends. Apportioning it among the 
two factors we get about 74 per cent determination by yield, 14 per 
cent by acreage, and 12 per cent joint determination, as the final 
estimate. 
