Probabilit y of a valve falling in a time period

1. Nov 15, 2007

1. The problem statement, all variables and given/known data

A large population of nominally identical "fail to close" control valves are put into service on the same day on similar installations. The number of valve failures per month N was recorded over time and shown to be given approximately by the following equation

Calculate the probability that the valve fails in the time period (0,24) months

2. Relevant equations

N = 0.001 X t^1.26 (failures/month)

3. The attempt at a solution

have tried it with the density function and the cumulative distribution function with N being lambda but still far away from the ans of 0.4414

The second part of the question also has be stumped as it states if the installation contains 3 valves in unrelated parts of the plant, calculate the probability that the installation is free of valve failure over the same time period (ans is 0.1743)

Last edited: Nov 16, 2007
2. Nov 15, 2007

HallsofIvy

Staff Emeritus
What was the question that 0.4414 is the answer to? I see no question given here!

What time period?

3. Nov 16, 2007