Re "Do the Math: Rooting Out Terrorists Is Tricky Business," Opinion, Jan. 19: John Allen Paulos' irrefutable argument about the dangers posed by retired Vice Adm. John M. Poindexter's Total Information Awareness system will cut no ice with the "innumerates" in the White House. Worse yet, recalculate the results for a more realistic 90%-accurate TIA system and the feds must arrest 29,999,900 (10% of 299,999,000 assumed nonterrorists) Americans in order to capture 900 real terrorists (90% of an assumed 1,000 total terrorists). A ratio of 900 terrorists to 29,999,000 innocents yields one terrorist for each 33,300 arrests.
Given these numbers, words like "jail" and "incarceration" seem misplaced. Not to worry: Poindexter can expropriate a term from another 20th century criminal to capture the essence of his policy: gulag.
Gordon D. Munro
Paulos shows dramatically how even a 99% accurate test will be overwhelmed by false positives when confronted with tiny a priori probabilities. But why not increase our chances a thousandfold by reducing the test population to those most likely to be involved in terrorism, young Arab men. We can do that, can't we?