Complaints time series significant change

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01mercy

Involved In Discussions
#22
In my experience this isn't unusual. The c chart can work but with the number of uses of various parts of the software that might generate complaints being susceptible to non-homogenous variation the I, MR chart is more likely a better indicator of stability - it certainly matches what our eyes tell us.

As Dr. Wheeler pointed out the c chart and p chart are subject to many 'assumptions' that are really requirements and so the I, MR chart is better choice.
Thank you for the advice @Bev D , with parts do you mean modular software? That is (not yet) the case. Unfortunately tagging of risk and complaint type is also not yet done but will be set-up soon because it is a mandatory requirement for our products as PMS activity. This in itself will bring ofcourse more insight and meaning to the complaint data.
 

Bev D

Heretical Statistician
Leader
Super Moderator
#23
Not knowing what the software is makes it difficult to be specific and correct. But the use of the software may be non-homogenously variable due to many factors: - from the number of uses to what the use cases are to the 'sensitivity' to complaining of the users.

You can also get the book from Amazon as a kindle book if you use kindle...
 

01mercy

Involved In Discussions
#24
Not knowing what the software is makes it difficult to be specific and correct. But the use of the software may be non-homogenously variable due to many factors: - from the number of uses to what the use cases are to the 'sensitivity' to complaining of the users.

You can also get the book from Amazon as a kindle book if you use kindle...
Yeah I saw that option but I don't use kindle, I prefer getting a copy of the book from SPC press :read:
 

01mercy

Involved In Discussions
#27
@Bev D @Steve Prevette can you tell me why you have chosen also for the I-mr-chart to be used since the count of complaint is descrete but this chart is pointed out to be used for continuous data?

As I understand correctly? the I-MR chart sets the control limits based on the variation in the Range between the points and the c-shart sets the limits based on the standard deviation over the individual measurements?
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Bev D

Heretical Statistician
Leader
Super Moderator
#28
In my reply on Friday I refer to two articles that Dr Wheeler wrote. The p chart and the I, MR chart. They should be highlighted in the post. This means that if you click on the word you will be directed to the article. (The words are links to the articles). The articles are free to read and explain the situation quite well. The I, MR chart actually works for any data type. If you still have questions after reading the articles let us know.
 

Steve Prevette

Deming Disciple
Leader
Super Moderator
#29
I default to the c-chart (which assumes a Poisson distribution) whenever I am counting events, defects, injuries. Most times (in my experience dealing with such data) each individual event is independent from each other. The closely related u chart also works well, for example, OSHA recordable injuries per 200,000 hours worked.

BUT in this case, the sum total of the complaint data showed a variation higher than the Poisson. Therefore, I tried the iMR chart (and probably woudl not be a bad idea to plot the R chart, but that usually ends up confusing folks more than enlightening them, IMO). Since it fit, I conclude that either there are "lumpings" of complaints (one initiating event begats multiple complaints), OR there is a mixture of different variations in the individual feeds. Thus, a good thing to do is start going down to the individual categories and sources of complaints to see what that tells you.

On the flow chart, I initially followed the "discrete data" path, then defects, then c-chart.
 

01mercy

Involved In Discussions
#30
In my reply on Friday I refer to two articles that Dr Wheeler wrote. The p chart and the I, MR chart. They should be highlighted in the post. This means that if you click on the word you will be directed to the article. (The words are links to the articles). The articles are free to read and explain the situation quite well. The I, MR chart actually works for any data type. If you still have questions after reading the articles let us know.
My apologies @Bev D I missed that, I will read it.
 
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