the Mean is where the highest number of individuals will fall statistically. The Units of Saidar an individual can wield is not what makes them "100" or "1" its the relative rarity of which that strength appears in nature. We do not have a single real number that maps an individuals actual strength in the power so we cannot do more than guess at this.

With that Said we can make the assumption that Lanfear is also 5.730729 SD from the Mean, but it doesn't tell us how much stronger she is than Morgase or the individual at the Mean. Or what number the Mean falls at on the scale.

Realistically Lanfear may be able to wield 1000 units of Saidar and Morgase 1 unit, but that tells us nothing of how many units the individual at the Mean can wield. RJ told us there is a Bell Curve distribution, but he gave us vague descriptions of actual power ... things like "considerably" or "very weak" but no indication of what that really means.

Personally I've placed the 21 level list as the Bell Curve, which would make the level 11 channelers at Mean with 10 SDs on each side (yes I know this isn't perfect). If you place all the FS at levels 20-21 and women of significant strength, from 16-19 you can then place Morgase at level 1 and the significantly weak channelers on levels 2-6 meaning AS all fall between 7-15 (levels 7 and 8 being Accepted). Which would square with the series quotes etc ... most AS will be Mean and below levels 9-11 or Daigian-Merilille (too weak to Travel) women AS consider strong falling at levels 12-15 or probably Verin-Moiraine in strength.

Another way to consider this is from RJs comments about levels

Forsaken Level ... Nynaeve, Sharina, the Forsaken

One Step Lower we have

"Exceptional"Level ... Egwene, Cadsuane, Bode, Nicola, Mielyn, Kerene

One step below that we have

"Very Strong" Level ... Moiraine, Siuan, Lelaine, Romanda, Elaida, Sheriam, Leane, and the other very strong Sisters like Kiruna, Bera and Galina I'd estimate that the weakest women at this range are likely Nesune, Katerine or Coiren.

Below that we have "Above average Sisters", women of influence in the Tower, but not at the very top rung ... likely Tarna or perhaps Masuri and Rafela at the top of this level, in the mid-range of that would be Verin, Seonid, Merana, Alana and someone like Merilille, Eldrith, Covarla etc.. at the lower range of the level

Middling sisters would encompass women like Adeleas and Vandene (who I would consider the MEAN level Channelers) This is where I believe the vast majority of the unnamed AS sit.

Weak Sisters would be women like Siuan and Leane are now, Cabriana, Kumira and, of course, Daigian.

Then there is the 37.5% of women who pretty much fall under the "negligible" category, I'd say there are actually many levels within this category ... New Moiraine, Alise, Sorilea, Morgase etc... perhaps Moiraine is 2x Alise who is in turn 3x Sorilea etc... but these are all Channelers of insignificant power. To do anything of real note they would need to have an angreal or lead a circle.

We can benchmark certain things at certain power levels such as Egwene level is about 2x Moiraine level, and that Moiraine level is about 3x Weak Sister level ... and we can assume that Weak Sister level is probably many times greater than even the highest level of "negligible" ... Daigian maybe 5x Sorilea who may be 15x Morgase ... but that doesn't really tell us a whole lot

Personally I think each level on the 21 level list comprises a smaller range of power (in terms of units) so Morgase level can wield 1 unit, but Sorilea's level may vary more and encompass women who can wield between 11-14 units, Alise level between 35-50 units, on the flip side level 21 may encompass women who can wield anywhere from 400-450 units, Level 20 would be women who can hold 365-400 units, that would allow for Graendal to be a 21 but still noticeably weaker than Lanfear, and Moghedien being at level 20 and still being much weaker than Lanfear, and also allows for Merana, Alana and Verin being on the same level and being unsure of which is stronger without an actual contest.