Polygraph lie-detector machines are commonly used in criminal investigations. The device measures nervous excitement, operating on the idea that if a person is telling the truth they will remain calm

• The American Polygraph Association claims that polygraphs accurately identify liars 90% of the time. In other words, if a person lied the test results will be positive 90% of the time.
• Although the polygraph test is good at identifying liars, there is a 50% chance that the polygraph test will say a truthful person is lying.

A police force wants to predict the accuracy of lie-detector tests for 1,000 suspected criminals. Assume that 700 per 1,000 suspected criminals tell the truth during polygraph tests.

Barber, N. (2013). Do Lie Detectors Work?Psychology Today. Retrieved from: https://www.psychologytoday.com/blog/the-human-beast/201303/do-lie-detectors-work

LieTruthRow TotalsTest result: negativePTest result: positiveQColumn totalso1000

What is the value ofQ?