Congratulations on passing your NSA polygraph! As you may be aware, three is a "magic number" for the NSA polygraph unit, as it is the number of times that they may subject applicants to polygraph interrogations at their own discretion, without authorization from above. By routinely subjecting applicants to more than one polygraph session, they ensure full employment for themselves.

By the way, there is no evidence that more experienced polygraphers produce more accurate results than less experienced ones. One wouldn't expect more experienced astrologers to produce more accurate results than less experienced ones, either. Some polygraphers may be better interrogators, just as some astrologers might be more skilled in the art of cold reading. But the problem in both cases is that the methodology employed lacks any scientific underpinnings. Your sense that the NSA's polygraph screening policy is arbitrary is absolutely correct.

Recently, I took the NSA polygraph for the third time.  I didn't expect to pass, but the examiner said the charts were clean this time.  That was a pleasant surprise, but I'm a bit perplexed.   

Granted, this time the examiner was more experienced, offered more reassurance, and explained what to do in more detail.  However it felt exactly the same way to me as the other times.

Oh well.  If I actually get the clearance I hope I don't have this much trouble in future check-ups.  I'll never blame anyone again for not wanting to take a polygraph, though.  It seems arbitrary.