assignable cause translation

Assignable Cause

Published: November 7, 2018 by Ken Feldman

assignable cause translation

Assignable cause, also known as a special cause, is one of the two types of variation a control chart is designed to identify. Let’s define what an assignable cause variation is and contrast it with common cause variation. We will explore how to know if your control is signaling an assignable cause and how to react if it is.

Overview: What is an assignable cause? 

A control chart identifies two different types of variation: common cause variation (random variation resulting from your process components or 6Ms ) and assignable or special cause variation.

Assignable cause variation is present when your control chart shows plotted points outside the control limits or a non-random pattern of variation. Since special cause variation is unexpected and due to some factor other than randomness, you should be able to assign a reason or cause to it.  

When your control chart signals assignable cause variation, your process variable is said to be out of control, or unstable. Assignable cause variation signals can be identified by use of the Western Electric rules, which include:

  •   One point outside of the upper control limit or lower control limit
  •   A trend of 6 or 7 consecutive points increasing or decreasing
  •   A cycle or repeating pattern
  •   A run of 8 or more consecutive points on either side of the average or center line.

Assignable cause variation can be attributed to a defect, fault, mistake, delay, breakdown, accident, and/or shortage in the process. Or it can be a result of some unique combination of factors coming together to actually improve the process. When assignable causes are present, your process is unpredictable. The proper action and response is to search for and identify the specific assignable cause. If your process was improved as a result of your assignable cause, then incorporate it so that the cause is retained and improvement maintained. If your process was harmed by the assignable cause, then seek to eliminate it.

3 benefits of an assignable cause

Assignable causes can be good or bad. They are signals that something unexpected happened. Listen to the signal.

1. Signals something has happened 

Special or assignable cause variation signals that something unexpected and non-random has occurred in your process.

2. Specific cause

By investigating and identifying the specific cause of your signal, you can narrow in on your next steps for bringing the process back into control.

3. Can become common cause variation 

Good news! You found that your assignable cause for lowered production was due to a power outage. Unfortunately, you may not be able to stop power outages in your community. If nothing is done, your assignable cause becomes a common cause. 

You might not be able to stop power outages, but could you install a back-up generator? Then, if the generator doesn’t kick on, you will have an assignable cause you can do something about.

Why is an assignable cause important to understand? 

Interpreting what an assignable cause tells you is important to understand. 

Provides direction for action

Since an assignable cause can be a signal of something good or bad, you need to understand the different actions. Don’t ignore special or assignable causes. 

Not every unusual point has an assignable cause 

While at your favorite casino, you may throw a pair of dice at the craps table. Is there an assignable cause for throwing an 11 or a 10, or is it random variation? No, you would expect the process of rolling a fair pair of dice to show 10s and 11s. What about a 13? That would be unexpected and probably the result of something unusual happening with the dice. The same is true for your process. Don’t assume an assignable special cause unless your control chart signals it. 

Useful for determining whether your improvements worked

When you improve the process, your control chart should send signals of special cause variation — hopefully in the right direction. If you can link that signal to the specific assignable cause of your improvement, then you know it worked. 

An industry example of an assignable cause 

The accounts receivable department of a retail chain started to get complaints from its customers about overbilling. Fortunately, the manager of the department had participated in the company’s Lean Six Sigma training and had been using a control chart for errors.

Upon closer review, she noticed that errors seemed to occur more on Fridays than the rest of the week. In fact, the chart showed that almost every Friday, the data points were outside the upper control limit. She was concerned that nobody was identifying that as a signal of special cause.

She put together a small team of clerks to identify why this was happening and whether there was an assignable reason or cause for it. The assignable cause was determined to be the extra work load on Fridays. 

The team recommended a change in procedure to better balance the workload during the week. Continued monitoring showed the problem was resolved. She also held an all-hands meeting to discuss the importance of not ignoring signals of special cause variation and the need to seek out an assignable cause and take the appropriate action.

3 best practices when thinking about an assignable cause 

Signals of special cause variation require you to search for and identify the assignable cause.

1. Document your search 

If you’ve identified the assignable cause, document everything. If this cause happens again in the future, people will have some background to act quickly and eliminate/incorporate any actions.

2. Quickly identify the cause 

Time is of the essence. If the cause is resulting in a deteriorating process, act quickly to identify and eliminate the cause. The recommendation is the same if your cause made the process better, otherwise, whatever happened to improve the process will be lost as time goes by.

3. Don’t ignore signals of assignable cause 

Even if you get a single signal of special cause, search for the assignable cause. You may choose not to take any action in the event it is a fleeting cause, but at least try to identify the assignable cause.

Frequently Asked Questions (FAQ) about an assignable cause

1. is an assignable cause always bad .

No. It is an indication that something unexpected happened in your process. It could be a good or bad thing. In either case, search for and identify the assignable cause and take the appropriate action. 

2. What are some sources of an assignable cause? 

Some sources may be your process components such as people, methods, environment, equipment, materials, or information. Your process variation can come from these items and can be the assignable cause of a signal of special cause variation.

3. How do I tell if I should look for an assignable cause? 

Control charts were developed to distinguish between common and special cause variation. If they signal special cause variation in your process, seek out an assignable cause and take the appropriate action of either eliminating or incorporating your assignable cause.

Final thoughts on an assignable cause

All processes will exhibit two types of variation. Common cause variation is random, expected, and a result of variation in the process components. Special cause variation is non-random, unexpected, and a result of a specific assignable cause. 

If you get a signal of special cause variation, you need to search for and identify the assignable cause. Once found, you will either seek to incorporate or eliminate the cause depending on whether the cause improved or hurt your process.

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Ken Feldman

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Encyclopedia of Production and Manufacturing Management pp 50 Cite as

ASSIGNABLE CAUSES OF VARIATIONS

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Assignable causes of variation are present in most production processes. These causes of variability are also called special causes of variation ( Deming, 1982 ). The sources of assignable variation can usually be identified (assigned to a specific cause) leading to their elimination. Tool wear, equipment that needs adjustment, defective materials, or operator error are typical sources of assignable variation. If assignable causes are present, the process cannot operate at its best. A process that is operating in the presence of assignable causes is said to be “out of statistical control.” Walter A. Shewhart (1931) suggested that assignable causes, or local sources of trouble, must be eliminated before managerial innovations leading to improved productivity can be achieved.

Assignable causes of variability can be detected leading to their correction through the use of control charts.

See Quality: The implications of W. Edwards Deming's approach ; Statistical process control ; Statistical...

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Deming, W. Edwards (1982). Out of the Crisis, Center for Advanced Engineering Study, Massachusetts Institute of Technology, Cambridge, Massachusetts.

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Shewhart, W. A. (1939). Statistical Method from the Viewpoint of Quality Control, Graduate School, Department of Agriculture, Washington.

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(2000). ASSIGNABLE CAUSES OF VARIATIONS . In: Swamidass, P.M. (eds) Encyclopedia of Production and Manufacturing Management. Springer, Boston, MA . https://doi.org/10.1007/1-4020-0612-8_57

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Assignable Cause

Last updated by Jeff Hajek on December 22, 2020

An assignable cause is a type of variation in which a specific activity or event can be linked to inconsistency in a system. In effect, it is a special cause that has been identified.

As a refresher, common cause variation is the natural fluctuation within a system. It comes from the inherent randomness in the world. The impact of this form of variation can be predicted by statistical means. Special cause variation, on the other hand, falls outside of statistical expectations. They show up as outliers in the data .

Lean Terms Discussion

Variation is the bane of continuous improvement . It decreases productivity and increases lead time . It makes it harder to manage processes.

While we can do something about common cause variation, typically there is far more bang for the buck by attacking special causes. Reducing common cause variation, for example, might require replacing a machine to eliminate a few seconds of variation in cutting time. A special cause variation on the same machine might be the result of weld spatter from a previous process. The irregularities in a surface might make a part fit into a fixture incorrectly and require some time-consuming rework. Common causes tend to be systemic and require large overhauls. Special causes tend to be more isolated to a single process step .

The first step in removing special causes is identifying them. In effect, you turn them into assignable causes. Once a source of variation is identified, it simply becomes a matter of devoting resources to resolve the problem.

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Lean Terms Leader Notes

One of the problems with continuous improvement is that the language can be murky at times. You may find that some people use special causes and assignable causes interchangeably. Special cause is a far more common term, though.

I prefer assignable cause, as it creates an important mental distinction. It implies that you…

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How to deal with Assignable causes?

How to deal with Assignable causes?

Across the many training sessions conducted one question that keeps raging on is “How do we deal with special causes of variation or assignable causes”. Although theoretically a lot of trainers have found a way of answering this situation, in the real world and especially in Six Sigma projects this is often an open deal. Through this article, I try to address this from a practical paradigm.

Any data you see on any of your charts will have a cause associated with it. Try telling me that the points which make your X MR, IMR or XBar R Charts have dropped the sky and I will tell you that you are not shooting down the right ducks. Then, the following causes seem possible for any data point to appear on the list.

  • A new operator was running the process at the time.
  • The raw material was near the edge of its specification.
  • There was a long time since the last equipment maintenance.
  • The equipment maintenance was just performed prior to the processing.

 The moment any of our data points appear due to some of the causes mentioned below, a slew of steps are triggered. Yeah – Panic! Worse still, these actions below which may have been a result of a mindless brain haemorrhage backed by absolute lack of data, results in more panic!

  • Operators get retraining.
  • Incoming material specifications are tightened.
  • Maintenance schedules change.
  • New procedures are written.

My question is --- Do you really have to do all of this, if you have determined that the cause is a common or a special cause of variation ! Most Six Sigma trainers will tell you that a Control chart will help you identify special cause of variation. True – But did you know of a way you could validate your finding!

  • Check the distribution first. If the data is not normal, transform the data to make it reasonably normal. See if it still has extreme points. Compare both the charts before and after transformation. If they are the same, you can be more or less sure it has common causes of variation.
  • Plot all of the data, with the event on a control chart.  If the point does not exceed the control limits, it is probably a common-cause event.  Use the transformed data if used in step 1.
  • Using a probability plot, estimate the probability of receiving the extreme value.  Consider the probability plot confidence intervals to be like a confidence interval of the data by examining the vertical uncertainty in the plot at the extreme value.   If the lower confidence boundary is within the 99% range, the point may be a common-cause event.  If the lower CI bound is well outside of the 99% range, it may be a special cause.  Of course the same concept works for lower extreme values.
  • Finally, turn back the pages of the history. See how frequently these causes have occurred. If they have occurred rather frequently, you may want to think these are common causes of variation. Why – Did you forget special causes don’t really repeat themselves?

 The four step approach you have taken may still not be enough for you to conclude if it is a common or a special cause of variation. Note – Any RCA approach may not be good enough to reduce or eliminate common causes. They only work with special causes in the truest sense.

So, what does that leave us with! A simple lesson that an RCA activity has to be conducted when you think even with a certain degree of probability that it could be a special cause of variation. To ascertain that if the cause genuinely was a Special cause all you got to do is look back into the history and see if these causes repeated. If they did, I don’t think you would even be tempted to think it to be a special cause of variation.

Remember one thing – While eliminating special causes is considered goal one for most Six Sigma projects, reducing common causes is another story you’d have to consider. The biggest benefit of dealing with common causes is that you can even deal with them in the long run, provided they are able to keep the process controlled and oh yes, the common causes don’t result in effects.

Merely by looking at a chart, I don’t think I have ever been able to say if the point has a Special cause attached to it or not. Yes – This even applies to a Control chart which is by far considered to be the best Special cause identification tool. The best way out is a diligently applied RCA and a simple act of going back and checking if the cause repeated or not.

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Translations

Context sentences, english russian contextual examples of "assignable cause of variation" in russian.

These sentences come from external sources and may not be accurate. bab.la is not responsible for their content.

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Assignable cause : meaning into german

Translation of "assignable cause" into german

Alphabetical index english words:.

  • assignability
  • assignation
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COMMENTS

  1. Assignable Cause

    Concepts Assignable Cause Published: November 7, 2018 by Ken Feldman Assignable cause, also known as a special cause, is one of the two types of variation a control chart is designed to identify. Let's define what an assignable cause variation is and contrast it with common cause variation.

  2. PDF The assignable cause The Control Chart Statistical basis of the control

    Statistical Process Control often takes the form of a continuous Hypothesis testing. The idea is to detect, as quickly as possible, a significant departure from the norm. A significant change is often attributed to what is known as an assignable cause. An assignable cause is something that can be discovered and corrected at the machine level.

  3. Assignable Cause

    Benefits of an Assignable Cause. The identification and management of assignable causes in a process or system offer several benefits: Improved Quality Control: Assignable causes pinpoint specific factors leading to variations or issues within a process. Addressing these causes allows for better control over the process, resulting in improved product or service quality.

  4. Common cause and special cause (statistics)

    Special-cause variation always arrives as a surprise. It is the signal within a system. Walter A. Shewhart originally used the term assignable cause. The term special-cause was coined by W. Edwards Deming. The Western Electric Company used the term unnatural pattern. Examples Common causes. Inappropriate procedures; Poor design

  5. ASSIGNABLE CAUSES OF VARIATIONS

    Assignable causes of variation are present in most production processes. These causes of variability are also called special causes of variation ( Deming, 1982 ). The sources of assignable variation can usually be identified (assigned to a specific cause) leading to their elimination. Tool wear, equipment that needs adjustment, defective ...

  6. Assignable Cause: Learn More From Our Online Lean Guide

    An assignable cause is a type of variation in which a specific activity or event can be linked to inconsistency in a system. In effect, it is a special cause that has been identified. As a refresher, common cause variation is the natural fluctuation within a system. It comes from the inherent randomness in the world.

  7. How to deal with Assignable causes

    Compare both the charts before and after transformation. If they are the same, you can be more or less sure it has common causes of variation. Plot all of the data, with the event on a control chart. If the point does not exceed the control limits, it is probably a common-cause event. Use the transformed data if used in step 1.

  8. assignable cause

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  11. ASSIGNABLE CAUSE

    Translation for 'assignable cause' in the free English-German dictionary and many other German translations. bab.la arrow_drop_down bab.la - Online dictionaries, vocabulary, conjugation, grammar Toggle navigation share

  12. assignable cause translation in German

    assignable cause translation in English - German Reverso dictionary, see also 'assign, assignee, assimilable, assignment', examples, definition, conjugation

  13. assignable causes

    English assignable causes in English dictionary assignable causes Sample sentences with " assignable causes " Declension Stem Match words I accepted this assignment ...' cause I believe in the merits of the government' s case opensubtitles2 I accepted this assignment ...' cause I believe in the merits ofthe government' s case opensubtitles2

  14. assignable causes

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  15. assignable cause definition

    1 to select for and appoint to a post, etc. to assign an expert to the job. 2 to give out or allot (a task, problem, etc.) to assign advertising to an expert. 3 to set apart (a place, person, time, etc.) for a particular function or event. to assign a day for the meeting. 4 to attribute to a specified cause, origin, or source; ascribe.

  16. Translation of "assignable cause" in Arabic

    Translations in context of "assignable cause" in English-Arabic from Reverso Context: I shall not fatigue the reader with a refutation of the logomachies which might be offered in explanation of this subject: of the contradiction inherent in the idea of value there is no assignable cause, no possible explanation.

  17. Translation of "assignable cause" into Amharic

    Translation of "assignable cause" into Amharic . ትውቅ ምክንያት is the translation of "assignable cause" into Amharic. Sample translated sentence: Do you obey the command to bear thorough witness, even if the assignment causes you some apprehension? ↔ የተጣለብህ ኃላፊነት የሚያስጨንቅህ ቢሆንም እንኳ የስብከቱን ሥራ በተሟላ ሁኔታ ...

  18. Translation of "assignable cause" into German

    Translation of "assignable cause" into German . zurechenbare Ursache is the translation of "assignable cause" into German. Sample translated sentence: These assignments caused a more intensive turn towards the differential geometry of curved surfaces. ↔ Diese Aufträge bewirkten eine intensivere Hinwendung zur Differentialgeometrie gekrümmter Flächen.

  19. assignable cause

    Translated by SHABDKOSH translator. Word by word cause कारण देना Other words assignable assignable cause - Meaning in Hindi Did you mean: assignable cause We are constantly improving our dictionaries. Still, it is possible that some words are not available. You can ask other members in forums, or send us email. We will try and help.

  20. ASSIGNABLE CAUSE OF VARIATION

    Translation for 'assignable cause of variation' in the free English-Russian dictionary and many other Russian translations. bab.la - Online dictionaries, vocabulary, conjugation, grammar share

  21. Assignable cause translation in German: zurechenbare Ursache

    Assignable cause: meaning into german. Translation of "assignable cause" into german. assignable cause - zurechenbare Ursache assignable - abtretbar - abtretungsfähig - angebbar - anweisbar - belegbar - bestimmbar - nicht übertragbar - übertragbar - zedierbar

  22. assignable

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  23. assignable cause in Hindi

    While the paranoiac " manages successfully to create external persecutory objects, the melancholic founders in a universe of misfortune with no assignable cause." 2. Other sculptures such as'An Absence of Assignable Cause '( 2007 ), Kher's bindi-bedecked envisioning of a sperm whale's heart, are sufficiently astonishing and allusive to make ...