[Edited 9/18/2018]  I’d been meaning to get back to the entry I started on grading children’s clothes before now. Returning to the previous discussion of the disparity in body size measurements between the CS151-50 and the ASTM D-5826 as well as the 40 year gap in study age, those differences might not be particularly significant for grading purposes. Not overtly. It’d matter if you were using either to draft but not grade. What matters for the purposes of discussion, is the difference between the itemized size measurements from one size to another. These are what’s known as grade rules. For example, if the chest of size 5 is listed as 23″ and the chest of size 6 is listed as 24″, you’d subtract the two to get the grade rule, namely 1″.

Returning to a comparison of the two studies, my analysis shows the ASTM rules are a bit off kilter. Maybe that’s just an opinion but when the rules of the CS151-50 are compared, the latter seem to be more stable. By stability, I mean that the sizes aren’t jumping inordinate amounts from size to size. Not so with ASTM. For example, the CS151-50 shows the armscye girth increasing by .5″ size to size. Since that standard is newer, with a better nourished sample group than the ASTM depression era study, one could rationally expect the ASTM study to show the same rate of growth… but it doesn’t. The ASTM data set shows the armscye girth to increase by 5/8ths. That seems odd and could mean that the standard is trying to catch up with what approximates a particular morphology more typical of today’s children.

If you want to jump ahead (recommended) and prepare yourself for the next part of the series of extrapolating grade rules, you’ll have to do a couple of things. One, download the data set courtesy of the WayBack Machine as the NIST link is dead. Two, enter all of those values in a spreadsheet. I tried to OCR it but couldn’t get it to work (well). If you’re a member of the forum, you can get the file I created in excel to save the bother of having to enter it all yourself. Once you have the spread sheet, subtract the measures from size to size to derive the grade rules (this is already done for you in the forum doc). After you’ve done that, we can discuss how these different rules are applied in designing your grade rules.

An aside:
If you actually follow these instructions (I wonder how many will) you’re likely to run into a couple of things that may puzzle you. I couldn’t decide when to include an explanation, now, or in the next entry. I think I’ll do it today. Just come back to this if you need to. This is in no particular order or significance:

Rate of grow for size 6x.
You may notice a drop off in the rate of grow for this size. This is due to a unique configuration of this sizing because 6X isn’t really a whole size such as that between 5-6 or any other size, but more like half of a size -of a still larger size- which is what we call a size break. For example, the armscye circumference grade for all sizes between 2-6 is 5/8th inch (ASTM data) but for 6X, it’s only 1/2″. Since 6X is a weirdly configured size preceding the size break of 7, for sizes 7-16, you could kind of call it a half size. If you don’t understand what I mean, don’t worry. Really. You should just know that if the rate of grow for the size 6X is less than the rate of grow for the other sizes, it’s not due to a math or sampling error.

Arcane measuring stuff:

• Height. The first thing to know is that height means something very specific. It means the measure from the floor up. This matters a great deal. When you read “waist height”, this means the height of the waist from the floor up.
• Cervicale refers to the seventh cervical vertebrae; the last of seven bones in your neck. If you move your chin toward your chest, this is the most prominent bone back there. This is a critical measuring point (see Fundamentals of fitting pp 163-166 of my book). Usually, cervicale is a measure down (opposite of height). Cervicale to waist etc, are measuring down from the neck to the waist.

Why the distinction matters:
In older data sets, not all measures were taken but you can extrapolate the measures you need if you understand the difference between height and cervicale measures. For example, in the CS151-50, the cervicale to hip measure wasn’t taken but you can make an educated guess by comparing the cervicale to waist, waist height and crotch height (also, cervicale to knee and knee height). This will make more sense if you’re looking at the charts or measuring illustrations.

Related:
Grading children’s clothes pt.1
What are grade specs, grade rules and grade rule libraries?
How to create grade rules 1
How to create grade rules 2
How to create grade rules 3