# Thread: order stat

1. ## order stat

X is a system that consists of three devices. The system would work correctly if at least one of the device works. Mean time for failure of each device are

beta1 = 75
beta2 = 50
beta3 = 25

life times are exponentially distributed

part a) find the density function for the lifetime of X

How can i find it please help.

2. Originally Posted by ilikec
X is a system that consists of three devices. The system would work correctly if at least one of the device works. Mean time for failure of each device are

beta1 = 75
beta2 = 50
beta3 = 25

life times are exponentially distributed

part a) find the density function for the lifetime of X

How can i find it please help.
You need to find the pdf of $X_{(3)} = \text{max} \, (X_1, \, X_2, \, X_2)$. One approach would be to use the method of distribution functions (which is certain to be explained somewhere in your class notes and textbook).

If you need more help, please show all your work and say where you are stuck.

Edit: In fact, I have just seen this thread http://www.mathhelpforum.com/math-he...tribution.html and your question is pretty much identical to what has been asked and answered there already.

Thread closed.