Question

Susan took two tests. The probability of her passing both tests is 0.6. The probability of her passing the first test is 0.8. What is the probability of her passing the second test given that she has passed the first test?

Answer 1

Answer: .75

Step-by-step explanation:

Let Pass1 and Pass2 be Susan passing test 1 and 2 respectively.

Let probability be denoted by P.

Then,

P( Pass1 and Pass2 ) = 60%

P( Pass1 ) = 80%

Now, probability of her passing the second test given that she has passed the first test is denoted by,

P( Pass2 | Pass1 )

This a conditional probability problem. So formula for it is,

P( Pass2 | Pass1 ) = P( Pass1 and Pass2 ) /

P( Pass1 )

P( Pass2 | Pass1 ) = 60% / 80%

= .75