## Does the NSA Think You're a Terrorist?

a terrorist? Does the NSA think you are When the NSA sorts through American communications to find terrorists, what is their accuracy in identifying one? CLASSIFIED One thing's for certain, No test on earth is 100 % accurate. False Positive: Let's assume the NSA's Terrorist 1 out of 100 an erroneous 'positive' diagnosis resulting from testing inaccuracies. test is 'positive results' will actually be negative. MISIDENTIFIED TRUE The test will accurately FALSE 99% of 'positive results' What does the NSA's Terrorist measure 99% of terrorists are terrorists. test do? who take it. This is a big difference and a common mistake True vs False positives mathematicians use Bayes Theorem Conditional probability of an "event A" given an "event B" EVENT EVENT Tested Positive by an Probability one is a Terrorist accurate NSA test How rare are terrorists in America? Marginal probability of occurrence of each event. 2001 2011 in just one decade if we assume there were 20 individuals involved per attack, that would mean there are ATTEMPTED TERRORIST414 ATTACKS TERRORISTS IN AMERICA per year there were 207 Within the United States American population over 13 years old. 258,458,870 ihat's an average of MARGINAL PROBABILITY American population that is a terrorist 207 per year 0.0001601802252% I in 624,297 Americans is a terrorist. CALCULATING TERRORISM WITH BAYES THEOREM American population that is a terrorist Probability of being a terrorist (low marginal probability) Pr(X|A) Pr(A) Pr(A/X) : ~A Probability of NOT being a terrorist (high marginal probability) Pr(X|A) Pr(A) + Pr(X|-A) Pr(-A) Let's do the numbers: 'Positive' Test Result .99 O 0.0000016 X\A |X|-A Pr(A|X) Probability 'Positive' Test Result given being a terrorist (Accurate test) (.99 O 0.0000016) (.01O 0.9999984) Probability 'Positive' Test Result given NOT being a terrorist (Inaccurate test) ACCURATE RESULT Probability of being a terrorist (A) given a positive test (X). 0.0001584 or 0.01584% (probability of being a terrorist given a 'positive' test result THIS IS WHAT WE WANT TO KNOW. likelihood of having found a terrorist with a positive test result 99.98416% Surprised? HIGHER THE RARITY, THE MORE FALSE RESULTS, FALSE POSITIVE probability of not being a terrorist given a 'positive' test result DESPITE AN ACCURATE TEST. MARGINAL PROBABILITY I in 100 I in 1,000 I in 100,000 1 in 100,000,000 20 40 80 50% 50% 9.0164% 90.9836% 0.0989% 99.9011% 0.0098 99.9902% ACCURATE FALSE POSITIVE ACCURATE FALSE POSITIVE ACCURATE FALSE POSITIVE ACCURATE FALSE POSITIVE In order for the NSA have a 94% PROBABILITY OF ACTUALLY FINDING A TERRORIST WITH A "POSITIVE" RESULT. they would need a test with 99.9999* ACCURACY ( equivalent to the accuracy of a DNA test.) HOW MANY FALSE POSITIVES HAVE THE NSA FOUND? WE KNOW THAT IN JUST PART OF 2013, the government requested access to over 30,000 WOULD BE FALSE POSITIVES which means 9862 that if each of these accounts Remember, 414 represented a suspected estimated terrorists of those (on average) in the last 10 years. terrorist... ACCOUNTS OF AMERICANS FROM JUST 3 COMPANIES APPLE FACEBOOK GOOGLE Dec 1, 2012 to May 31, 2013 in the first part of 2013 in the first part of 2013 the U.S. Government made between the U.S. Government made between the U.S. Government made between 4,000 to 5,000 20,000 to 21,000 8,000 to 9,000 info requests for Apple customer data info requests for U.S. based Facebook user data info requests for Google customer data When it comes to living online... NEVER. SAY. ANYTHING. SOURCES: Presented by: http://www.census.gov/popclock TOPCOMPUTERSCIENCEDEGREES.COM http://yudkowsky.net/rational/bayes https://www.facebook.com/about/government_requests https://www.apple.com/apples-commitment-to-customer-privacy https://kiwi.ecn.purdue.edu/rhea/index.php/Bayes theorem eg2 S13 http://www.google.com/transparencyreport/userdatarequests/countries/?t-table http://www.cchem.berkeley.edu/molsim/personal_pages/berend/news/sim131.pdf DEVELOPED BY N NOWSOURCING http://betterexplained.com/articles/an-intuitive-and-short-explanation-of-bayes-theorem http://www.start.umd.edu/start/publications/START IUSSDData TerroristAttacksUS_1970-2011.pdf

# Does the NSA Think You're a Terrorist?

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