There has been a great deal of controversy over the last sev

There has been a great deal of controversy over the last several years regarding what types of surveillance are appropriate to prevent terrorism. Suppose a particular surveillance system has a 99% chance of correctly identifying a future terrorist and a 99.9% chance of correctly identifying someone who is not a future terrorist. If there are 1000 future terrorists in a population of 300 million, and one of these 300 million is randomly selected, scrutinized by the system, and identified as a future terrorist, what is the probability that he/she actually is a future terrorist?

Solution

E(number nonterrorists identified as terrorists) = (.001)(299,999,000) = 299,999
E(number terrorists identified as terrorists) = (.99)(1000) = 990

P(identified as terrorist is actual terrorist) = 990/(990+299,999) = 990/300,989
= (approx) 1/304 = (approx) 0.3%

No. I would be \"uneasy\" about fascism no matter how accurate the surveillance system supposedly was. The calculation might make a few other people afraid, but most of the sheep don\'t care if (or how many) innocent people are victimized by the fascist authorities.

---
\"The probability relevant to you is 0.1 % - the probability of being unrightfully classified as future terrorist (if you are investigated). It is fairly low, I would say and perhaps a risk worth taking.\"

The other person responding demonstrates my point. They don\'t mind 299,999 people wrongly convicted of terrorism (possibly put to death) to catch 1000 terrorists. So we destroy the lives of (possibly murder) roughly 300,000 people to keep (at most) 5,000 people from being murdered? Forgive me for not wanting to live in such a country!

And the numbers I am using assume a level of accuracy which is impossible to come even close to in the real world. Reality is that even murdering 3 million innocents would not get rid of all the terrorists. And that does not take into account that a government destroying 3 million of its citizens will generate thousands, maybe tens of thousands, of new \"terrorists\".

I put terrorist in quotes, because at that point those working for the government are clearly the real terrorists, and those called terrorists by the government would be considered freedom fighters by any citizen who was not one of the sheep