Introduction

Fidelity is the degree to which a change is implemented as intended. Improvement project teams should measure fidelity, because if the change is not implemented, nothing will change. However, measurement resources are usually limited, especially in the early stages of implementation. A frequent problem in quality improvement is that people waste time collecting too much data. A previous paper1 showed how to demonstrate local gaps in care with very small samples of 5–10 patients. In evaluative clinical trials, the goal is to detect small differences between groups with precise estimates of these differences. By contrast, local quality improvement is often asking whether local performance meets a specific standard, such as 80% compliance with a guideline. If local performance is poor, small samples of 5–10 patients may be large enough to demonstrate a gap in care. In this paper, our goal is to offer some general guidelines to measuring fidelity of implementation on small samples in the face of constrained measurement resources.

Our target audience is healthcare improvers who have:

• Identified a local gap in care.

• Analysed the causes of this gap.

• Developed a change theory to address the gap.

• Created an initial change concept to be tested and refined locally.