[HN Gopher] Statistical process control after W. Edwards Deming ...
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Statistical process control after W. Edwards Deming (2020)
Author : Tomte
Score : 77 points
Date : 2021-08-25 08:52 UTC (1 days ago)
(HTM) web link (www.2uo.de)
(TXT) w3m dump (www.2uo.de)
| WWWWH wrote:
| This is a great article, but is there a good modern source (say
| an introductory text book) on these ideas?
|
| I've a vague memory of doing this as a first year undergraduate,
| but that was a long time ago. And stupidly, I didn't think I'd
| ever need them...
| Witoso wrote:
| I recommend "Understanding Variation: The Key to Managing
| Chaos" by Donald J. Wheeler, colleague of Deming. Good intro to
| SPC.
| Zigurd wrote:
| Deming wrote very accessible books. _Out of the Crisis_ is a
| general audience book but it covers statistical quality
| analysis in enough depth to understand how it works.
| winslett wrote:
| I stumbled upon Deming's "Out of the Crisis" when wandering
| through the library in school. It has changed how I thought about
| system improvement ever since.
|
| I use the things I learned for marketing, product, and
| engineering systems.
|
| Want to improve a system? Before doing anything, collect data and
| measure. A system must be stable, else you cannot improve it.
| Marketing campaigns. Funnel optimizations. Performance
| improvement.
|
| Most "stability" is achieved by simple things like squashing bugs
| (campaign bugs, performance bugs, or UX bugs).
|
| Once you achieve stability of output (i.e. low standard
| deviation), then improve the system.
|
| Simple, uh?
| marcosdumay wrote:
| Well, keep in mind that "improvement" here implies non-
| transformative change (we usually call this "optimization" on
| informatics). If you are not sure you have the correct system
| running, stabilizing it is the last thing you want.
| zepto wrote:
| > If you are not sure you have the correct system running,
| stabilizing it is the last thing you want.
|
| Stable in this case just means you are clear what the system
| is and can keep operating it if you want to.
|
| That is a prerequisite to evaluating the system in order to
| determine whether it is what you want.
| avs733 wrote:
| I think that may be a too narrow vision of "transformative"
| improvement.
|
| I worked in a factory where one of the biggest, and hardest,
| improvements we made was coaching the managers and engineers
| to _leave the technicians alone_ when they were doing
| maintenance.
|
| We collected data on how often they were interrupted, how
| much time it cost, and how interruptions could lead to RIT
| changes in procedures that affected quality.
|
| Previously the engineers and managers saw the checking as
| helping because they could se ethe status of things and
| observe and answer questions, many would even lend a hand.
| Oversight and engagement was seem as a path to improved
| quality. To let go of that was a huge transformation. It
| started with data - a lot of data - that allowed us to
| identify that weekend and night maintenance generally went
| faster and better.
| marcosdumay wrote:
| Well, I claim that is a way too broad definition of
| "transformative". The people kept creating the same
| products, by almost the same procedure.
| [deleted]
| xyzzy21 wrote:
| The products I design/sell generate the inputs for this kind of
| thing for the semiconductor industry.
|
| It always makes cocktail party conversation complicated.
| mch82 wrote:
| Out of curiosity, do you mean that your products generates
| template forms for collecting statistical sample data (like
| Minitab), or that your products collect measurements that are
| fed into tools like Minitab as data?
| Jtsummers wrote:
| The funnel experiment examples are interesting. The fourth case
| (T' = H) is a great example of normalization of deviance [0].
| Without a clearly communicated target to return to, you reliably
| shift further and further from that initial target, not even
| oscillating around the target like in the third case.
|
| [0] https://en.wikipedia.org/wiki/Normalization_of_deviance
| curiouscats wrote:
| Here are some online resources on Deming's ideas
| https://curiouscat.com/management/deming/online
| shitmonger wrote:
| Fuck you vax.
|
| Fuck your vax pass.
|
| Fuck you.
| s-luv-j wrote:
| >"You can not inspect quality into a product." ~Deming
|
| Yep. This applies double to software. Putting software under load
| and trending health measures to look for two standard deviations
| variance is very similar to how Deming instrumented production
| lines. The neat thing that software enables for both automobile
| manufacturing and software products themselves is that those
| exact same health measures can be trended and analyzed after they
| get into the hands of consumers.
|
| If your quality apparatus is purely inspection based, you will
| live your life one escalation to the next.
| onion2k wrote:
| I've spent much of the past few years trying to work out if
| this means I should stop relying on pull requests to catch
| problems, and put something in place ahead of writing code
| instead, but so far I've not figured out an alternative that
| works. If anyone has any ideas, _please_ share them.
| afarrell wrote:
| Pair-drafting pseudocode with a colleague into a Dropbox
| Paper document is a great way to evaluate tradeoffs.
| s-luv-j wrote:
| One of the reasons why pushing change straight to production
| with A/B testing works so well is that you can expose your
| new change to statistically significant real user load and,
| assuming your have decent instrumentation, find the problems.
| This does mean that a subset of your users get exposed to
| those problems.
|
| A more user friendly way would be to have a scaled down
| replica of production setup with simulators that mimic user
| behavior. Assuming the development team actually believes in
| and tends this environment, they will find the lion's share
| of bugs that commonly slip through peer review.
| Zigurd wrote:
| Deming is talking about repeatable manufacturing processes. The
| point of Statistical Process Control is that you sample metrics
| that tell you if the process will produce products reliably
| within tolerances.
|
| Software is completely different, it is hardly ever a
| repeatable process to create software. Making the same software
| over and over is nonsensical, but making a billion identical
| contact lenses is exactly what you want.
|
| There are forms of software "inspection," like pair
| programming, that amount to what Deming says you should not do
| in manufacturing: Inspect everything. But pair programming is
| pretty rare. Other practices like code review have been called
| into question. So it may still be true that you can't inspect
| your way to quality in software, but not for the same reasons
| that it is a bad idea in many cases in manufacturing.
| hikarudo wrote:
| > Software is completely different, it is hardly ever a
| repeatable process to create software. Making the same
| software over and over is nonsensical, but making a billion
| identical contact lenses is exactly what you want.
|
| I've heard it said like this: Creating a software is like
| developing a recipe for a cake. Baking thousands of cakes (a
| "manufacturing process") is what you do once you have the
| recipe. The two activities are very different.
| Jtsummers wrote:
| Kind of. We have to clarify what we mean by "creating a
| software".
|
| This seems to be rarely done in most discussions on
| processes for software development. The lack of information
| regarding this means that everyone gets to be right and
| angry at everyone else.
|
| Are you making novel systems? Then it's like developing a
| recipe for a cake. Are you making bog standard CRUD web
| apps? Then you're baking thousands of cakes.
|
| A lot of software _development_ sits somewhere in between
| these two extremes. It has repeatable, well-established
| portions that can be executed almost mechanically, and
| portions that require you to sit down and collaborate or
| really think about what you 're doing. How these balance
| out on a project determines what approaches are appropriate
| to even consider.
|
| Then there's software _maintenance_ (an unfortunately
| neglected aspect of software in many parts of this
| industry). Here the same consideration applies. Are you
| writing new software that 's really just generating new
| kinds of custom reports? That's rather mechanical, you may
| even be able to automate yourself out of a job. Or are you
| adding truly novel features, extending your document editor
| to support real-time networked collaboration?
|
| Software runs the full gamut so no statement about what
| software _is_ will ever be correct. We can only discuss the
| utility or applicability of processes once we specify which
| kinds of software activities we 're involved in.
| s-luv-j wrote:
| You are 100% right that measuring the process of creating
| software is a terrible application of statistical process
| control. See Jira.
|
| One way to look at how Deming/Shewart's work applies to
| software is to consider what happens when you apply their
| statistical analysis techniques to running software.
| hbarka wrote:
| The irony is that Deming's philosophy was much better received in
| Japan that in the United States. American cars were considered
| crappy during the 70s and 80s while the Japanese were iterating
| their quality practices. Deming was not the only philosopher-guru
| of manufacturing quality. There was Peter Drucker, Walter
| Shewhart (Shewhart cycle), Joseph Juran, Shigeo Shingo, Philip
| Crosby (quality is free, rework is costly), Taguchi (Taguchi
| methods), Ishikawa (fishbone). JIT, Kanban, Kaizen funny enough
| are Japanese manufacturing terms that have made its way into our
| programming dialect.
| hef19898 wrote:
| Also funny that the US defense industry was very close to some
| of these concepts during WW2. Only to have the Japanese adopt
| them really efficiently afterwards.
| neverartful wrote:
| My first job out of college (undergraduate) was working for a
| small consulting firm that did a lot of work in this area for the
| petrochemical industry and their suppliers. The owner had a PhD
| in decision sciences (statistics) and he did consulting work on
| statistical process control (SPC). This was my first exposure to
| this field and was so fascinated by it that after working there
| for a year, I quit my job so that I could go back to school full
| time and pursue a Masters degree in this area, but with focus on
| management information systems (MIS). Ironically, my work after
| graduate school has never touched on SPC or quality control.
|
| It's unfortunate that Deming (and many others) never really got
| the attention that their methods deserved.
| cafard wrote:
| Twenty-five or thirty years ago, one hear a great deal about
| total quality management (TQM).
| neverartful wrote:
| Yep, it was back in the early 1990s.
| Guthur wrote:
| I'm hoping that will change. I'm a big fan of Deming and
| Drucker, they've both got really insightful thoughts on
| business.
|
| My goal is to work more of Deming into knowledge work
| (software) to develop meaningful improvement into the process
| and product while leveraging Drucker for better effectiveness
| of the individual.
| mch82 wrote:
| Until recently, there hasn't been enough data to apply
| statistical process control in a lot of fields. Chemical
| process companies (like Kodak used to be) have used SPC. "Web
| scale" companies commonly talk about running experiments now.
| Lots of people talk about A/B testing, which is an extremely
| simplistic example of SPC. I've been anticipating more advanced
| SPC tools to replace A/B testing for years, but am not aware of
| any. Maybe I should have created one.
|
| Now I wonder if Machine Learning might pass up SPC as the
| primary method by which people identify and control key process
| variables.
| neverartful wrote:
| Actually, it does not take a huge amount of data to make use
| of statistical process control. In fact, it's so little that
| someone should be able to do it with paper, pencil, and
| calculator.
|
| The statistical technique I think that's better able to
| displace A/B testing is design of experiments (DOE). This
| approach also does not require that much data to implement.
| There was an excellent youtube series on it where the
| presenter used popping popcorn for his experiments. I can't
| seem to find it now.
| analog31 wrote:
| I've observed DOE in use. It's a statistical method at its
| core, and as such potentially suffers from the replication
| crisis.
| larrydag wrote:
| GE and other companies tried to implement Demings approach.
| They called it Six Sigma. Those that used Deming's concepts
| were successful. Yet too many misunderstood the idea of SPC and
| used in areas that was not meant for quality control. For
| instance trying to use SPC in the managerial process itself.
| eplanit wrote:
| Gawd, Six Sigma was an ever-present factor in all our work
| when I was at IBM in the late 80's to early 90's. I have
| complete respect for Deming, but when anything becomes
| "religion" it gets damaged or mis-used a lot, as you say.
|
| In our software group, we were constantly battling with
| management that wanted to start to look at software
| development as a factory-like process, and to apply factory
| QA processes.
| devonkim wrote:
| Cargo culting one's way to attempt obtaining results seems
| like the default approach of leadership unable to really
| adapt the proper lessons from other organizations and apply
| them to their own. If I as a person look up to a world
| class bodybuilder as a scrawny weakling, the solution to
| achieve that goal isn't to just eat like a bodybuilder but
| to train like one and that usually means dropping other
| activities like playing a bunch of video games (not that
| it's mutually exclusive - see Henry Cavill). But we as
| humans do the same thing all the time (how many people
| think of rich people in terms of consumption or some sets
| of personalities from popular media rather than to look at
| the data fully). However, there is a lot to learn and enjoy
| in the process, and companies that do well learn to have
| clear goals and processes that seem genuine and that
| employees can connect with. When people stop feeling this
| connection, they simply stop doing the habits at the
| individual (not working out, relapsing, etc) or disengage
| in organizations (burn out, disillusionment, etc)
| wheelinsupial wrote:
| I'm reading a book called Working Backwards about Amazon.
| There is a chapter on metrics and it says to use the DMAIC
| process, which comes from six sigma, for developing reporting
| and metrics. The authors provide an example about applying
| this to e-commerce at Amazon. They don't seem to use control
| charts, but they are still trying to examine the metrics for
| common vs special cause of variation.
|
| If you can relate inputs to the outputs of a process and you
| can get reliable data on the inputs, then you can use SPC in
| most areas. The costs to do so many not be worth it, however.
|
| Which managerial processes do you think this doesn't apply
| to?
| hef19898 wrote:
| Amazon, the Supply Chain part of it at least, has one of
| the best metrics systems I have ever seen in my life. Every
| metric is measuring something meaningful, each one is
| measuring a crucial process interface, each one is based on
| a simple calculation. Also most are measured in DPMO,
| looking at defects instead of things meeting expectations.
| The funny thing is, during my time metrics where presented,
| across all levels, in blunt, no chart, tables in a auto
| created PDF. And yet this is still light years ahead of
| everything else I saw, including fancy control towers.
| mch82 wrote:
| Six Sigma is to the field of Statistical Process Control what
| PowerPoint templates are to the field of graphic design. The
| biggest problem with Six Sigma is many of the people who roll
| it out understand how to follow the instructions in a Six
| Sigma book, but don't understand the underlying statistics
| well enough to recognize when the templates will fail or need
| to be changed.
| hencq wrote:
| Amen. The principles behind Six Sigma are solid. They're
| just a repackaging of Deming's SPC principles after all.
| However, too often it devolves into a box ticking exercise.
| That being said, in my experience just educating everyone
| in your organization on the basic principles (e.g. what Six
| Sigma would call yellow belt) tends to be quite valuable.
| Even without a lot of statistics, teaching people to first
| properly define a problem statement and emphasizing finding
| root causes before taking action tends to lead to better
| decision making.
| Zigurd wrote:
| Six Sigma is a travesty of statistical process control. For
| one thing, only rarely does a process attain six sigma
| reliability. Six Sigma is about cult-like in-group/out-group
| dynamics for the Six Sigma Black Belts.
| jihadjihad wrote:
| W. Edwards Deming is the source of one of my favorite quotes: _"
| In God we trust; all others must bring data."_
|
| One of the fascinating things about Deming's work is that Japan's
| automobiles went from being referred to pejoratively as "Jap
| Crap" to symbols of quality (Toyota, Honda, Subaru, Nissan,
| Mazda, etc.) within a short few decades--quite a feat for a
| nation struggling to regain its industrial footing after WWII.
| heymijo wrote:
| I'm curious what makes that your favorite quote.
|
| It gives me pause, mainly because I've seen it abused,
| ironically, often in contrast to some of Deming's core ideas.
|
| YMMV
| Tomte wrote:
| Deming used the quote, but did not coin it:
| https://quoteinvestigator.com/2017/12/29/god-data/
| User23 wrote:
| Deming gets the credit, but in Japan it was Homer Sarasohn[1][2]
| who did the foundational work[3]. In fact, he handed the reins
| off to Deming.
|
| One particularly interesting thing is that, at least once upon a
| time, Canon didn't even bother inspecting their copiers and
| printers, because the variance was so low it was a waste of
| time[4].
|
| [1] https://en.wikipedia.org/wiki/Homer_Sarasohn
|
| [2] https://honoringhomer.net/
|
| [3] https://apnews.com/article/e2908339e16a48dc8efe37d77a905daa
|
| [4] http://qualiticien.over-blog.com/article-679016.html
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