SRC Forum - Message Replies
Forum: Reliability & Maintainability Questions and Answers
Topic: Reliability & Maintainability Questions and Answers
Topic Posted by: Reliability & Maintainability Forum
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998
Posted by: JM Cloarec
Date posted: Tue Oct 28 22:57:59 US/Eastern 2003
Subject: MTBF assignment
Can we estimate a MTBF target like that :
reliability performance system is any failure should occur less than once per year. As the system is used 18h per day, the MTBF must be equal or greater to 6,570 h i.e (8,760 / 24) * 18.
Reply Posted by: BWD
Date Posted: Wed Nov 5 8:57:20 US/Eastern 2003
In the chi-square equation and the table, alpha is the risk factor and is 1 - the confidence level. So, a 90% confidence is a 10% risk factor which you use in the table to obtain a estimate for the one sided lower level MTBF. This answers the question of what value you need to meet the required reliability at 90% confidence.