I was answering this question for a quiz and apparently I got it wrong, although

Question

I was answering this question for a quiz and apparently I got it wrong, although I don't know where I went wrong in my math. Can anyone help?

A computer program is tested by 3 independent tests. When there is an error, these tests will discover it with probabilities 0.2, 0.3, and 0.5, respectively. Suppose that the program contains an error. What is the probability that it will be found by at least one test?

Here is what I did.
P(found by at least one test) = 1 - P(no tests discovered the error)
= 1- (1-0.2)(1-0.3)(1-0.5)
= 1-0.8*0.7*0.5
=0.72

And apparently that wasn't correct? Does anyone know where I went wrong?

Thanks,
Travis

Explanation / Answer

let A =error found by test 1 let B=error found by test 2 let C=error found by test 3 ------------------------------------------------------------------------- Given P(A)=0.2, P(B)=0.3, P(C)=0.5 therefore P(notA)=0.8, P(notB)=0.7, P(notC)=0.5 -------------------------------------------------------------------------- Note: tests are independent P(notA & notB & notC) =P(notA)*P(notB)*P(notC) =0.8*0.7*0.5=0.28 ---------------------------------------------------------------------------- P(found by at least one test) = 1- P(not found by any test) =1-P(notA & notB & notC) =1-0.28 =0.82

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.