ERROR TO CASES OF NORMAL DISTRIBUTION AND CORRELATION. 143 
division of the comumuity into p numerically equal classes. The table of double 
classification of values of L and of M will then contain p^ compartments ; and if we 
draw the figure corresponding to the division of the standard solid into p equal 
portions by parallel vertical planes, and shift this figure along its base through a 
Fig. 10. 
distance ctjual to D/ 27 r of its whole breadth (the part of the figure which pi ejects on 
one side being superposed on the other side, so as to leave the whole breadth 
unaltered), we obtain a diagram with jr compartments, whose areas are proportional 
to the numbers in the corresponding compartments of the table of double classifica¬ 
tion. 
