# Annual Failure Rate calculation

Experts,

I need assistance on what is the best way to present a device's annual failure rate.

I am reporting on devices by each month.  Fields are the following:

Month_year       Device_Name     Total Device        Failure Total     Failure Percentage
2014-01                3050 HDC         29559                      184           0.0747
2014-02                3050 HDC         30053                         55           0.022
2014-03                3050 HDC         30388                         21           0.0083

I only have data from January 2014, so I average the failure Percentage field?  Or calculate (sum (failure total) / sum (total device)) *100
Or something else..

Thanks
###### Who is Participating?

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Commented:
Realistically, report it any way you want.

Since they're asking you to make up data you can make up the answers as well.

More practically, I would average the failure percentage fields. At least it's easy to track that backwards and justify the value. If that's not what they want then they'll probably tell you.

Often people don't need what they are asking for. This is especially true of managers.
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Commented:
I'm not getting the same numbers you are.

According to my calculations the failure percentages are as follows:

29559      184      0.006224838
30053      55      0.0018301
30388      21      0.000691062

That being said, your method does work and should give you the most accurate representation of the data.
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Author Commented:
The formula I was using to get the percentage is (( failure/total) *12).
this worked because I was only reporting on the current monthly failure rate.  (told by management)

So now that they want to report on the Annualized failure rate, How should I write my formula?

Do I average the failure Percentage field?
Formula:  averaged comes to:  0.035

Or

calculate (sum (failure total) / sum (total device)) *100
Formula:   90000   /      260  = 0.288888889
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Author Commented:
Thanks.. you are right about that..
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