Question

you take a test, and 60% pass the first time and 40% fail. The second time around,80% pass the test and 20% fail. The third time, 90% pass and 10% fail. What is the probablilty that you pass on the 2nd time? What is the probability that you pass on the 3rd time? What is the probablity you fail? "

Answer 1

.95?

Answer 2

a) P(pass 2nd) = P(fail first) * P(pass second) = .4 * .8 = .32 or 32%

b) P(pass 3rd) = P(fail first) * P(fail second) * P(pass third) = .4 * .2 * .9 = .072 or 7.2%

c) P(fail) = .4 * .2 * .1 = .008 or 0.8%

Answer 3

Any help?

Answer 4

what if we assume that the person appearing in second test already failed teh first test?

Answer 5

work with a number and it will be easier

Answer 6

Thanks satellite73

Answer 7

@yellowlegoguy99 has it without a number, but if you get confused in a problem like this pick some large round number like1000 and work with that

Answer 8

but again a problem if we consider any number, should the number would remain same for all the test or we would be implying the percentage of failures in first test to the second time ?

Answer 9

i would assume that you only need pass the test once

Answer 10

means the failure will apply for the 2nd test right?

Answer 11

yes, see @yellowlegoguy99 answer above

Answer 12

What?

Answer 13

i was saying your answer above explains it

Answer 14

can you people also make me understand how to calculate break even?

Answer 15

say you have 1,000 people
600 pass
400 fail
out of the 400 who fail, 320 pass the second one
out of the 80 who fail the second one, 8 will fail the last one

Answer 16

Correct