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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

Russ Suter

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.

Maliki Hassani

ASKER

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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Russ Suter

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Maliki Hassani

ASKER

Thanks.. you are right about that..