Considerations when designing, analyzing, and reporting reliability studies

BACKGROUND: Reliability studies have a long history in the physical therapy literature and their sophistication has evolved over the decades. Often, however, there has been incomplete reporting or a lack of coherence among study purpose, design, choice of analysis, sample size justification, and reporting of results. Two possible explanations for this oversight are a vaguely written purpose statement and statistical software that does not provide all essential information. OBJECTIVE: The goal of this masterclass is to provide considerations and resources to assist investigators structure a coherent reliability study design and subsequent presentation of results. DISCUSSION: This masterclass highlights the importance of framing a study purpose that clearly distinguishes between a hypothesis testing and parameter estimation study and appropriately labelling the study design. It also stresses the importance of stating whether the raters are the only ones of interest or whether they are intended to represent a larger group of raters, applying a sample size calculation consistent with the study purpose, and reporting results that align with the study purpose and design.