Originally Posted by janetdoe

But roughly speaking, if 3% of screening encounters are randomly selected, and I go through the screening 10 times, then there is a (0.97)^10 = 73% chance that I will not be selected for even one of those encounters. There is a 22.8% chance that I will be selected for exactly one screening. The odds of being selected for 10 screenings is (0.03)^10 = 0.00000000000006 %.

There is definitely something non-random going on here. While I suspect the TSA's statistics are misleading, I wonder if the 'selected 10 for 10" guys are using a different definition of selection.

I think TSA's 3% definition is for situations where "we're only running the WTMD in this line, but every 30 or so people, we pick one person to go through the NoS or get an extra special pat-down." I have only had this happen to me once in the past year: the NoS was roped off, I watched a couple of dozen people go through the WTMD, and then I was selected to go through the NoS. This probably corresponds to about 1 in 30 trips for me, so I could buy a 3% statistic for that. I still think there is a biased selection by a TSO and this cannot be considered random.

The situation where two X-ray belts are feeding into one area that has both WTMD and NoS, and TSOs gesture at some people to go into one line or the other with no apparent logic - I think that is not considered random selection by the TSA, that's just 'sheeple direction'. Although it seems more truly random to me.

YMMV.