Hi,
JMP Books says like below, about Within Sigma Based on Average Moving Range
"If you do not specify a subgroup ID column, a constant subgroup size, or a historical sigma, JMP estimates the within sigma using the third method (moving range of subgroups of size two).
Within Sigma Based on Average Moving Range
Within sigma estimated by average moving range is the same as the estimate for the standard deviation for Individual Measurement and Moving Range charts", σst = Average Moving Range / d2(2).
It is called Subgroup Size 2, but it is expressed as Subgroup Size 1 in JMP. It may be based on Wheeler's Paper, etc., but in this case, I think it is more reasonable and clear to express it as Subgroup Size 2 rather than Subgroup Size 1.
QD 17.07 (spcpress.com)
Thanks
Ikju
