You are contradicting yourself. If a polygraph is 50/50, then its long-term accuracy rate would only be 50%. But you quote an expert as saying it is accurate between 70% and 90% of the time.Now YOU get it. The polygraph's accuracy is skewed by loaded questions, questions that are intended to give a neutral response, thereby proving the polygraph's accuracy/merit. "Is your handle LustyLad?", "Are you an alien?", "Have you murdered someone?", "Are you a male?" are the type of generic questions asked to establish a base for the polygraph. They know the answers in advanced (unless you have committed murder, are an alien, or don't identify as male), and expect you to respond in a like manner. And that raises the accuracy % of the test.
Another way of looking at it - if you can guess a coin flip correctly 70% of the time, then it's clearly not a 50/50 flip, it's a loaded coin. A fair or random coin will always revert to the mean of 50% heads and 50% tails over hundreds of flips.
If you don't understand that, there's really no point in going down this rabbit hole any further. An accuracy rate of between 70% and 90% clearly makes a polygraph test useful for many purposes, even knowing it isn't infallible. Originally Posted by lustylad
It's that 10%-30% inaccuracy that calls it all into question. It's when the polygraph is used to find specific info that the inaccuracies matter. "Have you robbed a bank" takes on a different meaning when being asked during a job interview test compared to being held as suspect.
Final thought: Even though Brennan answered "yes", we don't know if the polygraph registered his answer as "less than truthful" or not. Brennan thought he was a commie supporter, the polygraph might have said he was lying.