Where does PDSA come from?
PDSA grew out of the Shewhart cycle and was refined by W. Edwards Deming, who replaced "Check" with "Study" to stress learning from results rather than only inspecting them. It is the best-known version of the same loop as PDCA, and is the model behind the Institute for Healthcare Improvement's approach to testing changes.
What are the four steps of PDSA?
- Plan. State the objective, make a prediction ("if we do X, we expect Y"), and decide what data you will collect, who does what and where the test will run.
- Do. Carry out the test on a small scale, such as one shift, one line or one ward. Record what happened, including problems and surprises.
- Study. Compare the results with your prediction. Ask what you learned and why the outcome differed, if it did.
- Act. Decide what to do next: adopt the change, adapt it and run another cycle, or abandon it.
What is the difference between PDSA and PDCA?
| PDCA | PDSA | |
|---|---|---|
| Third step | Check the results | Study and learn from the results |
| Emphasis | Confirming the change worked | Testing a prediction and building knowledge |
| Common use | Manufacturing, lean, standard work | Healthcare, services, quality improvement |
In practice the cycle is the same, and teams use the names interchangeably.
When should you use PDSA?
Use it when you are unsure a change will work and want to learn cheaply. Run several small cycles, each building on the last, instead of one large rollout.
Example
A hospital ward wanted to cut late discharge paperwork. In the first cycle, one nurse tried a checklist with five patients, predicting every form would be complete by 10am. The study showed four of five were, and the missed one lacked a pharmacy sign-off. The team adapted the checklist, tried it across a full shift in cycle two, then adopted it for the ward.