From the article: "Nature reported that the first round of field tests had a 70 percent accuracy rate. From the available material it is difficult to determine

From the article: "Nature reported that the first round of field tests had a 70 percent accuracy rate. From the available material it is difficult to determine exactly what this number means. There are a couple of ways to interpret this, since both the write-up and the DHS documentation (all pdfs) are unclear." I'm glad he pointed this out. "This might mean that the current iteration of FAST correctly classifies 70 percent of people it observes -- which would produce false positives at an abysmal rate, given the rarity of terrorists in the population." But maybe this isn't so bad if it means that 70% of people aren't molested in the airport, at the cost of missing 30% of terrorists we would otherwise catch. I'm very okay with this: I see this as (1.73 * 0.7)-million happier citizens per day [1] and (0 * 0.3) additional terrorist incidents [2]. "The other way of interpreting this reported result is that FAST will call a terrorist a terrorist 70 percent of the time. This second option tells us nothing about the rate of false positives, but it would likely be quite high. In either case, it is likely that the false-positive paradox would be in full force for FAST, ensuring that any real terrorists identified are lost in a sea of falsely accused innocents." The author is too smart for his own good here. The second interpretation _should_ be "FAST will call a terrorist a terrorist 70 percent of the time. What's a false positive?" Those unfamiliar with statistics may incorrectly see it this way. Seventy percent of terrorists will be caught, so that means we'll be more than 3 times safer than we already are! Such statistical incompetence is also strongly correlated to politicians. I can't back that up, though, due to my statistical incompetence. [1] http://www.quora.com/How-many-people-fly-domestically-in-the-United-States-each-day http://www.quora.com/How-many-people-fly-domestically-in-the... [2] http://www.gather.com/viewArticle.action?articleId=281474978709836 http://www.gather.com/viewArticle.action?articleId=281474978...