Sample s/ze 

 rnj 



^of/o of c/?eck 

 sco//ne^ free 



10 



20 



30 

 40 

 SO 



7S 

 too 



I2S 

 ISO 



200 

 2 SO 

 300 

 44)0 

 SOO 

 600 

 TOO 

 800 



/,0OO 



/,SOO 

 2,000 ■ 



3,000 



4.O0O 

 5,000 



/O,OO0 



.9 .8 .7 .6 



CORRELATION COEFFICIENT 



VSS, OF CHART 



Starting on the lower right-hand graph with the ac- 

 curacy desired, move across to the line representing 

 the appropriate coefficient of variation. From this 

 point move up to the curve representing the number 

 of trees in the sale, thence across to the right-hand 

 axis of the alignment chart and establish a point. 

 Then begin on the left-hand graph with the appropriate 

 correlation coefficient, move up to the appropriate 

 cost ratio curve, then across to the left-hand axis 

 of the alignment chart and establish a second point o 

 Connect these two points with a straight line, and at 

 the point where this line intersects the central axis 

 of the alignment chart, read the sample size required. 



I .8.7.6 .5 .4 .3 

 COEFFICIENT (^VARIATION 



Figure E. — Graph and alignment chart showing first sample size needed for 



various accuracies, coefficients of variation, sale sizes, corre- 

 lation coefficients, and cost ratios. 



-22- 



