How to calculate the POFOD correctly?

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • cmrcm
    New Member
    • May 2007
    • 6

    How to calculate the POFOD correctly?

    Hi everyone, I got a question about the POFOD.
    Q1: Implementing modules by two way. 1: 4 errors in 1000 test cases; 2: 6 errors in 1200 test cases.

    I got the P1=4/1000=0.004 and the P2=6/1200=0.005. Is the method of P2 more reliable?

    Q2: Now implement modules by 1, if 1 failed 2 will take over. What's the POFOD?

    I got two answers for the POFOD.
    1: P=P1 * P2=0.004*0.005= 0.00002
    2: P=1-((1-P1)*(1-P2))=1-((1-0.004)*(1-0.005))=1-(0.996*0.995)=1-0.99102=0.00898
    I am confusing with the two answers, could any one tell me which one is correct?

    Thanks in advance!
Working...