Does PMWar portal has a wrong question and incorrect answer on "ControlLimits"?
Arvind TripathiDirector of PM/PMO| FlowserveIrving, Tx, United States
Please look at this question posted on "PMWar" section of PM.com (I have surmised it in simpler language to avoid the controversy on the question itself):
Q: Who decides "Control Limits" of a process?:
a- Project Manager
b- The stakeholders
c- Both of these
d- None of these
The posted answer says "c" Both of these. My take is based on years of learning and experience in Statistics, is that the correct answer is "d". The reason is that "Control Limits" (meaning Statistical Process Control Limits" are based on the "past performance of the process" only and NONE of the answers a,b, or c. Please share your thoughts on this topic. Thank you!
- Arvind, PMP & a veteran statistician :-) Saving Changes...
Arvind TripathiDirector of PM/PMO| FlowserveIrving, Tx, United States
Or you can pick up any text book on 'Statistical Process Control (SPC). Good luck! Saving Changes...
Markus KopkoAI Enabler for Project & Program Mgmt | Founder PMotion.ai / The PM
AI Coach| PMotion.aiHamburg, Hamburg, Germany
Hello Arvind,
i think there is a missunderstanding here. You refer to the "statistical process control limits and the SPC and you may be completly correct here (i have no glue to be honest cause i have not even thewhite belt in Six Sigma ... ;)).
However, the PMWar questions referring mor to PM and PMP knowledge and the question targets here the quality management KA and here espacially the control charts.
Here is the source out of PMBOK Guide; pg. 237:
"...
Control charts, are used to determine whether or not a process is stable or has predictable performance.
Upper and lower specification limits are based on requirements of the agreement. They reflect the maximum and minimum values allowed. There may be penalties associated with exceeding the specification limits. Upper and lower control limits are different from specification limits. The control
limits are determined using standard statistical calculations and principles to ultimately establish the natural capability for a stable process. The project manager and appropriate stakeholders may use the statistically calculated control limits to identify the points at which corrective action will be taken to
prevent unnatural performance. The corrective action typically seeks to maintain the natural stability of a stable and capable process. For repetitive processes, the control limits are generally set at ±3 s around a process mean that has been set at 0 s. A process is considered out of control when: (1) a data point exceeds a control limit; (2) seven consecutive plot points are above the mean; or (3) seven consecutive plot points are below the mean. Control charts can be used to monitor various types of output variables.
Although used most frequently to track repetitive activities required for producing manufactured lots, control charts may also be used to monitor cost and schedule variances, volume, and frequency of scope changes, or other management results to help determine if the project management processes are in control.
..."
And in addition here is the source out of the most popular PMP Exam prep book RITA's (pg. : 305)
" ...
Upper and Lower Control Limits" Controllimits are often shown as two dashed lines on a control chart. These limits are the acceptable range of variation of a processs or measurement's results. Control limits indicate what is stable versus unstable (out of control ) in the process. Every process is expected to have some variation in its results (e.g., each door anufactured will not be exactly the same size).
The project manager and RELEVANT Stakeholders need to analyze and evaluate what would be appropriate upper and lower controllimits for the metrics or standards related to quality for this project. Normally this range is calculated based on -l- 3 sigma or standard deviatons, but it can go as high as +l- 6 sigma (sigma and standard deviations are discussed later in this chapter). Data points within this range are generally thought of as "in control,' excluding the rule of seven (described Iater in this section), and are
an acceptable range of variation. Data points outside this range indicate the process is out of control,
The concept of controllimits is also important outside of a control chart. A project manager can have controllimits for many things. How about for a work package? Is one hour late in its delivery a problem? How about one day? Such controllimits help the project manager know when to take action.
..."
Did this help?
Regards,
Markus
www.projectmanagement.plus
...
1 reply by Arvind Tripathi
Jan 13, 2017 4:12 PM
Arvind Tripathi
...
Markus,
Response to your question is Yes and No. Yes, because PMBOK explanation given is correct and absolutely in line with published literature on "Control Limits of a process" It further confirms that 'd' is the right answer. Other stakeholders can use control limits as a guide but they are not the one who decide these limits.
No, on Control Limits of a work package etc. as that is NOT what the question is asking. When you start talking about the work package you are actually changing the question as it is talking to the "Process" Hope that helps.
Saving Changes...
Arvind TripathiDirector of PM/PMO| FlowserveIrving, Tx, United States
Hello Markus,
Thank you for your thoughtful response and providing the evidence from PMBOk. Most of the evidence supports that Control Limits come from calculating.: mean value + or- 3 sigma for upper and lower control limits. It also clearly states that stakeholders can use this to adjust the process based on these limits. SPC and PM are fully aligned on this topic and both should give the same answer 'D'. Only item that I do not agree with is the last statement on this write-up as it talks to a unique situation of using the same name but meaning something totally different. This is NOT a normally accepted definition of 'control limits' but unique to an organization in a limited sense.
...
1 reply by Arvind Tripathi
Dec 15, 2015 12:51 PM
Arvind Tripathi
...
Thanks Markus!
PMBOK portion of your response is correct and I agree with it 100% but RITA's exam prep book portion contradicts PM-BOK statements right above it. And that is where lies our problem.
Saving Changes...
fosco frongiaSenior project manager| ENTE PATRIMONIALE CHIESA GESU' CRISTO SUGFino Mornasco, Como, Italy
hello Arvind,
first of all consider I'm Italian speaking so, probably, my English translation couldn't be the correct one.the first concept we have to consider is that specific limits (defined by the tolerance) have not statistical or mathematical relation with control limits. these last ones can be defined in different ways (for instance, we have control chart where the control limits are defined on the basis of 3 sigma or, in other cases, on the basis of the probability -I don't know if this is the correct translation - this last system is more used in Europe).
In other word we can define the control limits in accordance with:
a) our needs
b) the characteristics of the process we are analyzing
This is the reason because i affirm that the control limits SHOULD be defined by experts (has the PM or "normal" stakeholder the knowledge for doing it?).
Literature: I cannot suggest to you any literature in English because the documents I learnt are in Italian.
The second sentence was not deducted by the question but it was only an example.
many thanks for your suggestion Saving Changes...
Markus KopkoAI Enabler for Project & Program Mgmt | Founder PMotion.ai / The PM
AI Coach| PMotion.aiHamburg, Hamburg, Germany
Hello Arvind,
thx for your response. Like i said, i am no expert in statisticly theorys and/or processes ... for me, while i am laerning for PMP and also in daily practice it was totally clear and plausibel, that the control charts and its values where defined by the experts and than adjust along the process baes on the upcoming results.
If you that convinced, that PMBoK Guide and PMI is wrong here, well than you may should contact the team what is actually working on the PMBoK Guide 6th edition and make a suggestion for correction.
Regards,
Markus
...
1 reply by Arvind Tripathi
Jan 13, 2017 4:25 PM
Arvind Tripathi
...
Good idea Markus!
I would like to take up your suggestion and reach out but I do not see an issue anywhere in PMBOK, just in the PMWar question and it's correct answer. The PMBOK explanation on this is clear and correct. Do you know how I reach out to PMWar question producers? Thanks for your active participation in this dialogue.
Saving Changes...
fosco frongiaSenior project manager| ENTE PATRIMONIALE CHIESA GESU' CRISTO SUGFino Mornasco, Como, Italy
hello Arvind,
first of all consider I'm Italian speaking so, probably, my English translation couldn't be the correct one.the first concept we have to consider is that specific limits (defined by the tolerance) have not statistical or mathematical relation with control limits. these last ones can be defined in different ways (for instance, we have control chart where the control limits are defined on the basis of 3 sigma or, in other cases, on the basis of the probability -I don't know if this is the correct translation - this last system is more used in Europe).
In other word we can define the control limits in accordance with:
a) our needs
b) the characteristics of the process we are analyzing
This is the reason because i affirm that the control limits SHOULD be defined by experts (has the PM or "normal" stakeholder the knowledge for doing it?).
Literature: I cannot suggest to you any literature in English because the documents I learnt are in Italian.
The second sentence was not deducted by the question but it was only an example.
many thanks for your suggestion Saving Changes...
fosco frongiaSenior project manager| ENTE PATRIMONIALE CHIESA GESU' CRISTO SUGFino Mornasco, Como, Italy
hello Arvind,
first of all consider I'm Italian speaking so, probably, my English translation couldn't be the correct one.the first concept we have to consider is that specific limits (defined by the tolerance) have not statistical or mathematical relation with control limits. these last ones can be defined in different ways (for instance, we have control chart where the control limits are defined on the basis of 3 sigma or, in other cases, on the basis of the probability -I don't know if this is the correct translation - this last system is more used in Europe).
In other word we can define the control limits in accordance with:
a) our needs
b) the characteristics of the process we are analyzing
This is the reason because i affirm that the control limits SHOULD be defined by experts (has the PM or "normal" stakeholder the knowledge for doing it?).
Literature: I cannot suggest to you any literature in English because the documents I learnt are in Italian.
The second sentence was not deducted by the question but it was only an example.
many thanks for your suggestion
...
1 reply by Arvind Tripathi
Jan 13, 2017 4:20 PM
Arvind Tripathi
...
Fosco,
Thank you for your response and actually your English is quite good. Your answer based on the definition of Control Limits from +/- 3 Sigma is absolutely correct and consistent with PMBOK and other literature on Six Sigma and Quality. I agree with it.
However, you explanations under (a) and (b) are just interpretations based on an individual or their understanding of the English language. It has no basis in PMBOK as it does not say anywhere (th the best of my knowledge) that Stakeholders decide Control Limits.
Saving Changes...
Arvind TripathiDirector of PM/PMO| FlowserveIrving, Tx, United States
Dec 14, 2015 12:48 PM
Replying to Arvind Tripathi
...
Hello Markus,
Thank you for your thoughtful response and providing the evidence from PMBOk. Most of the evidence supports that Control Limits come from calculating.: mean value + or- 3 sigma for upper and lower control limits. It also clearly states that stakeholders can use this to adjust the process based on these limits. SPC and PM are fully aligned on this topic and both should give the same answer 'D'. Only item that I do not agree with is the last statement on this write-up as it talks to a unique situation of using the same name but meaning something totally different. This is NOT a normally accepted definition of 'control limits' but unique to an organization in a limited sense.
Thanks Markus!
PMBOK portion of your response is correct and I agree with it 100% but RITA's exam prep book portion contradicts PM-BOK statements right above it. And that is where lies our problem. Saving Changes...
Arvind TripathiDirector of PM/PMO| FlowserveIrving, Tx, United States
Dec 13, 2015 6:47 AM
Replying to MAEN QADDOURAH
...
answer is B
OK. But why do you say that B is the answer. i provided my rational for why D is the right answer. Saving Changes...
Arvind TripathiDirector of PM/PMO| FlowserveIrving, Tx, United States
Dec 14, 2015 6:41 AM
Replying to Markus Kopko
...
Hello Arvind,
i think there is a missunderstanding here. You refer to the "statistical process control limits and the SPC and you may be completly correct here (i have no glue to be honest cause i have not even thewhite belt in Six Sigma ... ;)).
However, the PMWar questions referring mor to PM and PMP knowledge and the question targets here the quality management KA and here espacially the control charts.
Here is the source out of PMBOK Guide; pg. 237:
"...
Control charts, are used to determine whether or not a process is stable or has predictable performance.
Upper and lower specification limits are based on requirements of the agreement. They reflect the maximum and minimum values allowed. There may be penalties associated with exceeding the specification limits. Upper and lower control limits are different from specification limits. The control
limits are determined using standard statistical calculations and principles to ultimately establish the natural capability for a stable process. The project manager and appropriate stakeholders may use the statistically calculated control limits to identify the points at which corrective action will be taken to
prevent unnatural performance. The corrective action typically seeks to maintain the natural stability of a stable and capable process. For repetitive processes, the control limits are generally set at ±3 s around a process mean that has been set at 0 s. A process is considered out of control when: (1) a data point exceeds a control limit; (2) seven consecutive plot points are above the mean; or (3) seven consecutive plot points are below the mean. Control charts can be used to monitor various types of output variables.
Although used most frequently to track repetitive activities required for producing manufactured lots, control charts may also be used to monitor cost and schedule variances, volume, and frequency of scope changes, or other management results to help determine if the project management processes are in control.
..."
And in addition here is the source out of the most popular PMP Exam prep book RITA's (pg. : 305)
" ...
Upper and Lower Control Limits" Controllimits are often shown as two dashed lines on a control chart. These limits are the acceptable range of variation of a processs or measurement's results. Control limits indicate what is stable versus unstable (out of control ) in the process. Every process is expected to have some variation in its results (e.g., each door anufactured will not be exactly the same size).
The project manager and RELEVANT Stakeholders need to analyze and evaluate what would be appropriate upper and lower controllimits for the metrics or standards related to quality for this project. Normally this range is calculated based on -l- 3 sigma or standard deviatons, but it can go as high as +l- 6 sigma (sigma and standard deviations are discussed later in this chapter). Data points within this range are generally thought of as "in control,' excluding the rule of seven (described Iater in this section), and are
an acceptable range of variation. Data points outside this range indicate the process is out of control,
The concept of controllimits is also important outside of a control chart. A project manager can have controllimits for many things. How about for a work package? Is one hour late in its delivery a problem? How about one day? Such controllimits help the project manager know when to take action.
..."
Did this help?
Regards,
Markus
www.projectmanagement.plus
Markus,
Response to your question is Yes and No. Yes, because PMBOK explanation given is correct and absolutely in line with published literature on "Control Limits of a process" It further confirms that 'd' is the right answer. Other stakeholders can use control limits as a guide but they are not the one who decide these limits.
No, on Control Limits of a work package etc. as that is NOT what the question is asking. When you start talking about the work package you are actually changing the question as it is talking to the "Process" Hope that helps. Saving Changes...
