Depending on the nature of the improvement you are seeking to implement, there are a number of different improvement methodologies you can use either individually or together.

On this page we will look at model for improvement, PDSA, experience based co-design, lean and six sigma, and theory of constraints.

Model for improvement

After using driver diagrams to discover what you want to change, the model for improvement is the approach, which will help you identify, carry out and evaluate the changes you make.

There are three initial questions every project should ask when developing their model.

  1. What are we trying to accomplish?

    – Identify an area for improvement and use this to establish a specific aim – remember to be as SMART as possible (specific, measurable, achievable, realistic, and time-bound). For example,
    for a patient falls reduction project, the aim might be ‘to reduce patient falls on Ward A by 50% within six months.’
    – Determine what or who will be affected by this change
    – Give your project a deadline.

  2. How will we know that a change is an improvement?

    – There are three types of measurement:
    – Outcome measures, eg number of patient falls occurring;
    – Process measures, eg reviewing the reliability of processes that may have an impact on the aim;
    – Balance measures to check unintended consequences, eg for a falls reduction project staffing levels may be a useful balance measure.

  3. What changes can we make that will result in improvement?

    – Get creative to develop ideas about how the improvement will be driven. Potential changes can be discovered using the driver diagram explained in the last section.
    – Remember, not all changes will result in an improvement. One change on its own may not achieve your aims.

Now time to PDSA

Plan, Do, Study, and Act is an effective method that helps teams plan the actions for their model, test it on a small scale, and review before deciding how to continue. It comprises four steps:


Using PDSA cycles are a fantastic way of taking ideas, trying them in practice, learning what works and what doesn’t to help you achieve success. You can broaden the scale of the test or adjust your ideas through more than one PDSA cycle – it may take a few before the idea starts to work reliably.

learning from data

Hints and tips

Experience based co-design

This is an approach that enables staff and patients (or other service users) to work in partnership to co-design services and/or care pathways.

In depth interviewing, observations and group discussions identify key touch points – aspects of the service that are emotionally significant.

A short film is created from the patient interviews, which is shown to staff so they can see how patients experience the service. Staff and patients are then brought together to review the findings and to work in small groups to identify and implement activities that will improve the service or the care pathway.

Throughout the process the focus is on experience and emotions rather than attitudes and opinions – using storytelling to identify opportunities for improvement.

Hints and tips

The Kings Fund has developed this toolkit to support effective use of this approach.

Lean/Six Sigma

Lean and Six Sigma are two methods that can be used together to provide a co-ordinated improvement approach and are effective tools to solve problems.

Lean focuses on the breadth of a process, aiming to improve end-to-end ‘flow’ and reduce waste within a process.

Six Sigma focuses on achieving an in-depth understanding of parts of a process in order to reduce variance and defects.

There are similarities:
• They have exactly the same objective: continuous business process improvement.
• Follow a structured approach to identify the root causes of a business problem and find the optimal solution to avoid recurrence of the problem.

And differences:
• Six Sigma improves the capability of steps that do add value whereas Lean focuses on eliminating waste.
• Six Sigma is a data driven methodology, whereas Lean relies more on value stream maps and subsequent analysis.

Hints and tips

Download more about these methods.

Theory of constraints

Theory of Constraints is an approach that shows how you can manage bottlenecks and their associated constraints. A bottleneck determines the pace at which the whole process can work, whilst the constraint is the bit of kit or resource that causes the bottleneck.

By identifying where the constraints are, it is possible to focus improvement effort and day to day operational management in order to maintain and increase throughput. The Theory of constraints identifies a five-step process to achieve continuous flow and improve throughput:

theory of constraints

Hints and tips

Whichever method(s) you use, it is vital you have a:
• Clear aim of what you are seeking to achieve and a realistic timeframe to achieve it
• A process to measure the outputs of your improvement project so you know whether the change has
been an improvement.

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