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 Post subject: 20 components and the probability of failure of an individuaPosted: Fri, 13 Jul 2012 23:27:36 UTC
 S.O.S. Newbie

Joined: Fri, 13 Jul 2012 23:23:44 UTC
Posts: 2
An electronic system containing 20 components and the probability of failure of an individual component is 0.15.
It is assumed that the components fail intermittently from one another.
a) What is the probability of failure of 2? And at least 1?
b) If one of them knows that has already failed, what is the probability of failure of at least two?
c) If at least one of them has failed, what is the probability of failure of at least two?

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 Post subject: Re: 20 components and the probability of failure of an indivPosted: Sat, 14 Jul 2012 02:49:57 UTC
 S.O.S. Oldtimer

Joined: Fri, 27 Jul 2007 10:17:26 UTC
Posts: 278
Location: Chandler, AZ, USA
I'll get you started on the first one:

Number of ways to choose 2 bad components out of 20 = .

That leaves 18 good ones , so

.

Now for , you could add , but there's an easier way by first finding

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 Post subject: Re: 20 components and the probability of failure of an indivPosted: Sat, 14 Jul 2012 02:50:23 UTC
 Moderator

Joined: Mon, 29 Dec 2008 17:49:32 UTC
Posts: 6007
Location: 127.0.0.1, ::1 (avatar courtesy of UDN)
clau wrote:
An electronic system containing 20 components and the probability of failure of an individual component is 0.15.
It is assumed that the components fail intermittently from one another.
a) What is the probability of failure of 2? And at least 1?
b) If one of them knows that has already failed, what is the probability of failure of at least two?
c) If at least one of them has failed, what is the probability of failure of at least two?

What do you mean by "components fail intermittently from one another"?

_________________

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 Post subject: Re: 20 components and the probability of failure of an indivPosted: Sat, 14 Jul 2012 03:44:00 UTC
 S.O.S. Newbie

Joined: Fri, 13 Jul 2012 23:23:44 UTC
Posts: 2
Forgiveness is not intermittent is independent, the most important question that I need are b) If one of them knows that has already failed, what is the probability of failure of at least two?
c) If at least one of them has failed, what is the probability of failure of at least two?

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