16 
BULLETIN 1488, U. S. DEPARTMENT OF AGRICULTURE 
Figure 12, may be obtained by dividing the difference between the 
maximum and minimum strength by the average strength, and multi- 
plying this result by 100. As an illustration, take curve No. 8 in 
Figure 11: 79 pounds (maximum strength on curve) minus 68.5 
pounds (minimum strength on curve) equals 10.5 pounds (difference). 
Dividing 10.5 by 73.7 (the strength found on the 50 per cent vertical 
line) and multiplying this result by 100 gives 14.25 (per cent extreme 
variation for this particular grade). This method is applicable to 
any grade. 
STRENGTH 
IN OUNCES 
SINGLE 
STRAND TEST 
24 
20 
A 
/ 
\ 
* 
j 
• 
\ 
/ 
/ 
\ 
S 
H 
1 leached and 
mercerized 
\ 
1 
/r^ 
Gray - 
// 
\ 
/ / 
s% 
\ 
4* 
eached 
^nalej 
s 
^V 
/ 
987654321 
GRADE NUMBERS 
Fig. 9. — Strength in ounces per single strand as determined by 32 observations of each grade of 
28s two-ply yarn spun from eastern upland cotton. (21.1 turns per inch in yarn.) The mercer- 
ized yarns were stronger than the gray and the gray yarns were stronger than the bleached 
The percentage of breaks below a specified magnitude or standard 
may be read from these curves. As an illustration, take Figure 12 
and read on horizontal 100-pound line to the intersection of No. 1 
curve and down on a vertical line through this point, which shows 
that 21 per cent of this grade broke below the given magnitude, 
100 pounds. Similarly, other percentages of breaks may be read. 
In judging the relative values of yarns it is important to know the 
percentage of these low breaks as well as their distribution. 
The average deviation is determined by averaging the differences 
between each item and the average (disregarding plus and minus 
