Sampling in quality improvement research

Sampling decisions directly affect the credibility, interpretability, and usefulness of quality improvement data. A scoping review recently examined how sampling methods and sample size considerations are conceptualised and justified within healthcare quality improvement initiatives. It systematically addresses sampling as a distinct methodological issue in quality improvement.

Recognising that quality improvement relies on timely, context-sensitive data rather than traditional statistical inference, the study aimed to identify and synthesise existing sampling strategies, frameworks, and methodological guidance used in quality improvement initiatives, situating these within the broader fields of evidence implementation and implementation science. 

The scoping review found that non-probability sampling methods, particularly judgment, purposive, and convenience sampling, dominate quality improvement practice due to their feasibility and alignment with rapid-cycle improvement approaches such as PDSA. Probability sampling is used selectively when generalisability or benchmarking is required. 

The review also found that sampling decisions in quality improvement are frequently underreported, inconsistently applied, or poorly justified. Few sources provided actionable frameworks for choosing or justifying sampling approaches. In the absence of fit-for-purpose frameworks, practitioners rely heavily on pragmatic, non-probability approaches shaped by local constraints, which increases the risk of bias, underestimation of variation, and reduced transparency—limiting cross-initiative learning, scalability, and confidence in improvement outcomes.

Sampling decisions have a direct impact on the credibility, interpretability, and applicability of quality improvement findings. The findings of the scoping review demonstrate the need for clearer, fit-for-purpose guidance to support transparent, methodologically sound, and context-sensitive sampling decisions in quality improvement. 

The scoping review, Sampling methods and considerations in quality improvement, is available in Issue 1 for 2026 of JBI Evidence Implementation