Ken and Technetters, Poisson statistics apply here.  Go to a table or nomograph of the cumulative Poisson distribution, which are likely to be in a quality or reliability engineering handbook.  

I checked the one on page 35 of O'Connor's Practical Reliability Engineering, 3rd edition, and generated this small table.

X       Y
74      0
147     1
203     2
285     5

Lou Hart, CRE 

----------
From:   Ken Patel[SMTP:[log in to unmask]]
Sent:   Friday, March 24, 2000 12:45 PM
To:     [log in to unmask]
Subject:        [TN] Realiability info: Failure rate with confedence level

Reliability/Quality Guru,
I received this question from our engineering department.

Currently, they are seeing 1 system crash out of 10 times. They want to
improve the crash rate to 1 failure every 30 times with 90% confidence
level. They want to know how many operation "X" they will run with no more
than "Y" failures with 90% confidence level which will yield 1 failure every
30 times.

I do not know how to solve it as haven't practiced it. Am I providing enough
information or what information is needed to make a sense out of it? What
kind of model it will fit, Poisson, Binomial, etc?

Any help will be highly appreciated.

re,
ken patel


______________________________________________________
Ken Patel                       Phone:  (408) 490-6804
1708 McCarthy Blvd.             Fax:    (408) 490-6859
Milpitas, CA 95035              Beeper: (888) 769-1808

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