I'm trying to calculate the probabilities and expected number of failures for data where my input is the mean time between failures.
So I have a list of things that are like:
- A - 10 days
- B - 35 days
- C - 720 days
- D - 1500 days
And I would like to figure out the following results:
- what is the probability for any component that it will fail today, this week, this month, this year?
- what is the expected number of failures for this month, this year?
Figuring this out for the base of days is reasonably easy.
Unfortunately, for the time being I am constrained to Excel, and for the larger periods, something like 0.5 ^ 1500 return 0. Not 0.00000001 but 0, making further calculations impossible.
So I was thinking to make my base a year or something, but I can't get my head wrapped around the proper calculations. I probably want to do something with the exponent, which would solve the rounding issues, but I can't figure out what.
I've read the similar questions and answers, but they all recommend the mathematically correct way, which due to rounding issues won't work for me.