science

PDCA

PDCA is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand PDCA rather than just read about it. In short: PDCA (plan–do–check–act), sometimes called plan–do–check–adjust is an iterative design and management method used in business for the control and continual improvement of processes and products. It is also known as the Shewhart cycle, or the control circle/cycle.

Key takeaways

PDCA belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PDCA to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PDCA from memory before moving on to harder problems.

Reference excerpt

PDCA (plan–do–check–act), sometimes called plan–do–check–adjust is an iterative design and management method used in business for the control and continual improvement of processes and products. It is also known as the Shewhart cycle, or the control circle/cycle. Another version of this PDCA cycle is OPDCA. The added O stands for observation or as some versions say: "Observe the current condition." This emphasis on observation and current condition has currency with the literature on lean manufacturing and the Toyota Production System. The PDCA cycle, with Ishikawa's changes, can be traced back to S. Mizuno of the Tokyo Institute of Technology in 1959. The PDCA cycle is also known as PDSA cycle (where S stands for study). It was an early means of representing the task areas of traditional quality management. The cycle is sometimes referred to as the Shewhart / Deming cycle since it originated with physicist Walter Shewhart at the Bell Telephone Laboratories in the 1920s. W. Edwards Deming modified the Shewhart cycle in the 1940s and subsequently applied it to management practices in Japan in the 1950s. Deming found that the focus on Check is more about the implementation of a change, with success or failure. His focus was on predicting the results of an improvement effort, studying the actual results, and comparing them to possibly revise the theory.

Meaning

Plan Establish objectives and processes required to deliver the desired results.

Do Carry out the objectives from the previous step.

Check During the check phase, the data and results gathered from the do phase are evaluated. Data is compared to the expected outcomes to see any similarities and differences. The testing process is also evaluated to see if there were any changes from the original test created during the planning phase. If the data is placed in a chart it can make it easier to see any trends if the plan–do–check–act cycle is conducted multiple times. This helps to see what changes work better than others and if said changes can be improved as well. Example: Gap analysis or appraisals

Act Also called "adjust", this act phase is where a process is improved. Records from the "do" and "check" phases help identify issues with the process. These issues may include problems, non-conformities, opportunities for improvement, inefficiencies, and other issues that result in outcomes that are evidently less-than-optimal. Root causes of such issues are investigated, found, and eliminated by modifying the process. Risk is re-evaluated. At the end of the actions in this phase, the process has better instructions, standards, or goals. Planning for the next cycle can proceed with a better baseline. Work in the next do phase should not create a recurrence of the identified issues; if it does, then the action was not effective.

About Plan–do–check–act is associated with W. Edwards Deming, who is considered by many to be the father of modern quality control; however, he used PDSA (Plan-Do-Study-Act) and referred to it as the "Shewhart cycle". The PDSA cycle was used to create the model of know-how transfer process, and other models. The concept of PDCA is based on the scientific method, as developed from the work of Francis Bacon (Novum Organum, 1620). The scientific method can be written as "hypothesis–experiment–evaluation" or as "plan–do–check". Walter A. Shewhart described manufacture under "control"—under statistical control—as a three-step process of specification, production, and inspection. He also specifically related this to the scientific method of hypothesis, experiment, and evaluation. Shewhart says that the statistician "must help to change the demand [for goods] by showing [...] how to close up the tolerance range and to improve the quality of goods." Clearly, Shewhart intended the analyst to take action based on the conclusions of the evaluation. According to Deming, during his lectures in Japan in the early 1950s, the Japanese participants shortened the steps to the now traditional plan, do, check, act. Deming preferred plan, do, study, act because "study" has connotations in English closer to Shewhart's intent than "check".

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with PDCA

Start with the simplest possible case. Write down what PDCA claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to PDCA before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about PDCA ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of PDCA

In research: PDCA appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses PDCA in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: PDCA is common in secondary-school and first-year university syllabi. It links to neighbouring topics American inventions, Project management techniques, Quality management, so understanding it makes those chapters shorter.
In everyday life: Look for PDCA outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study PDCA in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PDCA means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain PDCA out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PDCA in simple terms?

Why does PDCA matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study PDCA?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on PDCA.