Whatever it is, it should be consistently applied. I use 100 with 15 equaling one standard deviation because that’s what PFR uses. I figure if someone is reading a niche site like ours, he or she probably is already familiar with index scores.

Alternatively, someone used to looking at data might prefer a base of 50 with 10 equaling one SD.

I like a manifold display of stats. Showing raw numbers, adjusted numbers, marginal stats, and index scores together gives a fuller picture, I think.

I just boils down to personal preference. I don’t think there’s a “best” way to do it. I favor the school grade scale over the IQ scale simply because I’ve spent a lot more time dealing with grades than IQ scores.