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How accurate should government surveillance be? In 2013, it was revealed that the U.S. government was secretly monitoring its citizens’ phone calls and internet traffic through a program called PRISM. The goal was to identify potential threats and catch would-be terrorists.

In this lesson, students calculate conditional probabilities to determine the likelihood of false-positives and false-negatives, and discuss the tradeoffs between safety and accuracy.

### Students will

• Model related probabilistic events using Venn diagrams
• Apply Bayes Theorem given conditional probabilities
• Use probabilities to predict the consequences of a real-world policy

### Before you begin

Students should have a solid grasp of simple theoretical probabilities before beginning.