But how many of those have 15+ years experience of programming in C and C++?
35% was the average score for the original sample. Unfortunately, I do not recall the standard deviation, which would paint a better picture. A part of the test verification that I am doing is to find out the stats for this test.
My estimate is that IRO 1 in 20 applicants in the original sample had 15+ years of C/C++.