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Topics: Quality
How to quantify the reduction in reliability after defect repair in a product ?
Network:753



Many times during execution of project work, we carry out defect rectification for the problems highlighted by Control Quality / Validate Scope process. After the corrective action, the defect is repaired and it pases the internal/customer inspection. Will the reliability of this repaired product be same over its operating life as that of a product that is First Time Passed in all inspection stages? It certainly won't be same. But is there any way to quantify the reduction in reliability due to defect repair?
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Network:1017



Gorakhanath -

It really depends on the nature of the defect and resulting repair. If a defective component is replaced by a functional one (e.g. swapping a blown fuse for a good one), there should be no reduction in reliability. If the fix is more of a workaround or involves reusing the same component, then there might be some reduction in lifetime or performance which results.

Quantifying it will be a function of:

1. Figuring out what you want to measure - is it the effective working life of the product, mean time between failures or some other metric?
2. Gathering a baseline of data from a statistically representative sample of widgets which have had no defects
3. Gathering data from a statistically representative sample of widgets which were repaired
4. Comparing the two using a test such as a two sample t-test (assuming the populations follow a normal distribution)

Kiron
Network:1640



First, you have to define what quality means to your organization. Second, somebody have to define the quality attributes for the product. As project manager, you are not accountable for that. You are only accountable for managing all related activities to assure that product quality attributes have been achieved. That´s all that you can do as project manager. All related to product (except the activities to create it) are responsability of the business analyst
Network:1812



I agree with Sergio, This looks like an issue of ongoing operation process as reliability concern.
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1 reply by GORAKHANATH WANKHEDE
Oct 22, 2017 11:23 PM
GORAKHANATH WANKHEDE
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OK..so, product reliability engineer's inputs would be more fruitful here to provide link between defect repairs during manufacturing and MTBF during operational usage.
Network:753



Thank you Mr Kiran & Mr Sergio for detailed insight.
Network:753



Oct 22, 2017 11:07 PM
Replying to Riyadh Salih
...
I agree with Sergio, This looks like an issue of ongoing operation process as reliability concern.
OK..so, product reliability engineer's inputs would be more fruitful here to provide link between defect repairs during manufacturing and MTBF during operational usage.
...
1 reply by Sergio Luis Conte
Oct 23, 2017 5:04 AM
Sergio Luis Conte
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It is a matter of quality. Between other things your organization have to decide on which phase of quality to invest: quality assurance or quality control.
Network:1640



Oct 22, 2017 11:23 PM
Replying to GORAKHANATH WANKHEDE
...
OK..so, product reliability engineer's inputs would be more fruitful here to provide link between defect repairs during manufacturing and MTBF during operational usage.
It is a matter of quality. Between other things your organization have to decide on which phase of quality to invest: quality assurance or quality control.

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