Individual Control Chart

[#1]

here you find 54 individual data, exponentially distributed.

JMP analyses the data and provides a STRANGE Control Chart

Why?

See the attached file

Fausto Galetto

[#2]

Welcome to the community.  Sorry I can't provide specific feedback as your post lacks context.  You have attached a Word document with a data set and an X, MR chart.  Someone who was analyzing the data must have run (requested) that control chart platform.  If the data is in a logical series (e.g., time) and you don't have any rational subgroups, then looking at the data with that chart is a good idea.  Control charts do not assume any particular distribution to use them.

[#3]

Dear statman,

thank you for your reply.

I try to give you some more information:

1. the 54 numbers are UTI (Urinary Tract Infection)
2. collected in a Hospital
3. they are SINGLE data to be analysed as INDIVIDUALS
4. it is asked to assess if the "process" providing the data is IC (In Control) or OOC (Out Of Control)
5. the data distribution is EXPONENTIAL

In my opinion, the JMP Control Chart, shown in my attached file, is misleading... 

Your statement

• "Control charts do not assume any particular distribution to use them."

is not suitable.

faustoG

[#4]

What does this mean:  "it is asked to assess if the "process" providing the data is IC (In Control) or OOC (Out Of Control)"

Is this a homework problem?  How was the data collected?  Is it in a time series?  Is it in any rational order?  If not, then perhaps X, MR charts are not appropriate.  You can do some distributional analysis for outliers, but IC and OOC implies a rational series of(e.g., time).

Do you understand the meaning of IC and OOC?  Both of these are a function of how the data was collected and what comparisons are being made.  For example, an X, MR chart compares short-term variation as estimated by the range of consecutive data points (and shown as control limits on the X chart) to long term variation the X's plotted on the chart.  If you were to have rational subgroups, the charts would compare within subgroup variation to the between subgroup variation.

For distributional assumptions related to control chart method (or lack thereof), please see:

Shewhart, Walter A. (1931) “Economic Control of Quality of Manufactured Product”, D. Van Nostrand Co., NY

Wheeler, Donald, and Chambers, David (1992) “Understanding Statistical Process Control” SPC Press (ISBN 0-945320-13-2)

[#5]

Dear statman, Super User

1. it is NOT homework!
2. You seem to think I do not know Control Charts
3.  I actually have a "profound" (see Deming!) knowledge of the THEORY of Control Charts
4. and I know the books that you cite
5. so that I can state that the JMP analysis of the data is WRONG!
6. I know well the meaning of IC and OOC!

I am not familiar with using JMP, so I started by analyzing the data in my file.

I wrote a letter to JMP (Chiappa) signaling the BIG problem that the CC made by JMP is WRONG!

Mr. Chiappa (of JMP) suggested asking the Community to get the answer....

I did it.

• There is NO within subgroup variation and between subgroup variation; the data are INDIVIDUALS and must be analysed as such

IF YOU do not understand that the CC is wrong YOU cannot help me (new user of JMP)

faustoG

[#6]

While I agree with statman's comments about additional context, I do think we can speculate a bit more here.  If we assume that the data is in fact in a correct time series order, then the control charts don't look strange to me.  It appears that something changed near the end of the series and appears to be "out of control."  The precise meaning of "out of control" will depend on that missing context - I don't know much about urinary tract infections or about what exactly is being measured here, but there is a clear point at which what is being measured deviates significantly from the rest of the series.

I don't understand what you mean by the distribution is "exponential."  I also don't understand your comment that the distribution-free control chart is "not suitable."  I also don't understand what you find "STRANGE" about the control chart.  Perhaps you can elaborate on those 3 points.

[#7]

Dear dlehman1

Level V

YOU say:

• there is a clear point at which what is being measured deviates significantly from the rest of the series.

That point depends on the WRONG analysis by JMP.....

See my reply to statman.

YOU say:

• I don't understand what you mean by the distribution is "exponential."

You have to read some probability books and look for "exponential distribution."

YOU say:

• I also don't understand your comment that the distribution-free control chart is "not suitable." 
• I also don't understand what you find "STRANGE" about the control chart.

See my reply to statman: the JMP Control Chart is WRONG!

I am not familiar with using JMP, so I started by analyzing the data in my file.

I wrote a letter to JMP (Chiappa) signaling the BIG problem that the CC made by JMP is WRONG!

Mr. Chiappa (of JMP) suggested asking the Community to get the answer....

I did it.

.. and  I am waiting for somebody tells me how to analyse correctly the data, using JMP

I am eager to learn how to do that with JMP

Yesterday |  Posted in reply to message from faustoG 10-03-2024

I don't understand what you mean by the distribution is "exponential."  I also don't understand your comment that the distribution-free control chart is "not suitable."  I also don't understand what you find "STRANGE" about the control chart.  Perhaps you can elaborate on those 3 points.

[#8]

@faustoG
Instead of telling everyone in this discussion they are wrong, you could perhaps provide the analysis you have done on the data ?
That would help other members of the forum understand the differences between your results and the outcomes from JMP control chart.

Please keep calm and stay respectful.

[#9]

Dear  Victor_G

Super User

Thank you

I am calm and respectful.

Did you read my attached file?

IF NOT, please, read it and notice that I wrote to JMP about the WRONG Control Chart:

1. I am not familiar with using JMP, so I started by analyzing the data in my file.
2. I wrote a letter to JMP (Chiappa) signaling the BIG problem that the CC made by JMP is WRONG!
3. Mr. Chiappa (of JMP) suggested asking the Community to get the answer....
4. I did it.
5. .. and  I am waiting for somebody tells me how to analyse correctly the data, using JMP
6. I am eager to learn how to do that with JMP

 I do not have my solution:

I want to find the TRUE CC, with EXPONENTIALLY distributed data using JMP!

I do not tell the JMP Community they are wrong: I tell all of them that the analysis (made by JMP that you can find in my file) is WRONG: it does NOT consider that the data are EXPONENTIALLY distributed.

• WHY all think that this point is NOT important?

faustoG

[#10]

Ok, some points to answer and clarify (I did look at your file) :

1. The letter is written in Italian. As I don't speak/write/understand Italian (and many other users in the Forum may be in a similar situation) I may be lacking some context crucial to the understanding of the problem.
2. You mentioned a BIG problem, but never explains how/why/what is the problem. How/why is the calculation of control chart and/or control limits wrong ? Is it because few samples are detected out of the control limits calculated (and you were expecting more) ? What are your expectations/results ? Do you have specifications limits you would like to compare to (since you seem to imply the goal of the analysis is to check the measurement process) ?
3. I would suggest reading the post from @jthi Getting correct answers to correct questions quickly. This post will help you frame the questions so that the discussion can lead to a solution for you. In this example, we don't have any reference/analysis to compare to the one from JMP, and this last one (JMP) isn't satisfying for you. We will never be of any help if we don't know what you're looking for, and/or if you don't provide an example of the analysis and the "correct" answer/results you expect.
4. In the meantime, since you don't seem to be familiar with JMP and how the calculations are done, you can read the documentation about the Control Chart Builder.

No need for exclamation points, bold sentences and words and capital letters in your post, please avoid them.

We are a respectful Community of JMP Users, willing to help any JMP users in our free time. If you can't respect other people, nobody is going to help you.

Hope that you can specify your context, correct answer and analysis in more details so that we can all focus on the statistical part.