I don't care about my NSS, that was quite a while ago. I am just trying to figure out the merits of it, and more or less curious as to how the whole thing came together. Don't assume that I have a vested interest in it.
edit: I'll add that I don't have the NSS forumla in front of me, but am curious how the Navy decided to use this. Did anything in the formula change with MPTS or did NSS stay pretty much the same (with the minor correction for the value changes assoc. with MPTS)?.
Kmac - The answer to your question is the NSS formula is basically the same as it has always been. It is simply a T-score. That's a statistical term. Google it and you can read how it works.
I don't recall what the specific formula was before MPTS, but I don't believe it used 10% TGI and 90% grades. I think it was 100% grades. Mostly because in the old days, there was no flexibility in what maneuver could be flown when, so the total graded items was the same for everyone.
Where the big difference comes in is the grades themselves. MPTS uses a performance standard grading system. Some say it came from the USAF, but it has its roots in the civ world long before the USAF. Before NSS, there was no performance standard. Guidance to IPs about what a "below", "average", or "above" was consisted of "you know it when you see it."
Why does the Navy use NSS? Because it is a cheap, quick, and easy way to rank students. The ranking is used for selection. Since it just takes grades and there is no subjective input, it is theoretically less subject to outside criticism (like a member of congress asking why their voter's son Johnny didn't get jets).
Why does the Navy use MPTS? Because it sets "objective" standards of performance (unlike the old "above", "average", and "below"). The drive to MPTS got a big boost awhile back when someone said they weren't treated fair, a senator got involved, and it cost a very good admiral a very good job.