# Probability

• Sep 27th 2009, 07:01 PM
hydride
Probability
Positive test result-
Did not lie_______Lie
----------------------
15_____________42
(false pos.)____(true pos.)

Negative tes result-
Did not lie________Lie
----------------------
32______________9
(true neg.)_____ (false neg.)

If four of the test subjects are randomly selected without replacement, find the probability that, in each case, the polygraph indicated that the subject lied.

Thanks!
• Sep 28th 2009, 05:49 AM
The Second Solution
Quote:

Originally Posted by hydride
Positive test result-

Did not lie_______Lie
----------------------
15_____________42
(false pos.)____(true pos.)

Negative tes result-
Did not lie________Lie
----------------------
32______________9
(true neg.)_____ (false neg.)

If four of the test subjects are randomly selected without replacement, find the probability that, in each case, the polygraph indicated that the subject lied.

Thanks!

There are 98 subjects and the polygraph has said that 15 + 42 = 57 of them lied (positive result). So the required probability will be (57/98)(56/97)(...)(...) = ...