Question

A boiler has five identical relief valves. The probability that any particular valve will open on demand is 0.93. Assume independent operation of the valves. Calculate P(at least one valve opens). (Round your answer to eight decimal places.)

Answer 1

0.930000

Explanation:

Answer 2

There is a 99.99998% probability that at least one valve opens.

Explanation:

For each valve there are only two possible outcomes. Either it opens on demand, or it does not. This means that we use the binomial probability distribution to solve this problem.

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

`P(X = x) = C_(n,x).p^(x).(1-p)^(n-x)`

In which
`C_(n,x)` is the number of different combinatios of x objects from a set of n elements, given by the following formula.

`C_(n,x) = (n!)/(x!(n-x)!)`

And p is the probability of X happening.

In this problem we have that:

`n = 5, p = 0.93`

Calculate P(at least one valve opens).

This is
`P(X \geq 1)`

Either no valves open, or at least one does. The sum of the probabilities of these events is decimal 1. So:

`P(X = 0) + P(X \geq 1) = 1`

`P(X \geq 1) = 1 - P(X = 0)`

So

`P(X = x) = C_(n,x).p^(x).(1-p)^(n-x)`

`P(X = 0) = C_(5,0).(0.93)^(0).(0.07)^(5) = 0.0000016807`

Finally

`P(X \geq 1) = 1 - P(X = 0) = 1 - 0.0000016807 = 0.9999983193`

There is a 99.99998% probability that at least one valve opens.