Originally Posted by

**ehallison**
We don't know the chances of being selected, but it's much less than 50/50. I'm guessing about a 10% rate (which seems within the realm of possibility based on my experience, and my husband's previous experience). My probability calculating skills are a little rusty, but if we assume 1/10 chance of being chosen, then the chances of being chosen 7 out of 8 random tries are miniscule: .00001% or 1 in 100 thousandths percent. (1/10 7 times, times 9/10)

So I'm still skeptical that it's random.

Originally Posted by

**televisor**

Yes, that's a perfect example of randomness.

Note, I don't think your combinatorics are quite correct. You'd probably want to multiply that by 8, since the non-selected event could have happened at any of 8 positions, i.e. 8 permutations. But it's a bit late for me so I might be being stupid right now.

It has been way to many years since Probability and Statistics, so I am not even going to try for a precise analysis. Suffice it to say that the odds of 7 searches happening over 8 trials is very low indeed. I'd give the odds of being searched at less than 5%. So

**ehallison**'s numbers are probably on the high side

(if one could say that with a straight face).

But lets stay with the 10% odds of being searched at any one entry. So there is a 90% chance of not being searched. The odds of not being searched seven consecutive times is around 47% if my late-night math skills are working. I'd say that most of us beat those odds, but we don't question whether the randomness of the situation exists.

When dealing with probabilities and extremely large numbers of travelers, all sorts of anomalies/outliers will exist. The rare person who gets a bunch of secondaries, and the rare one who has never gotten one.