the factors or conditions that cause differences (variation) in data, measurements, or outcomes within a study or process. These can arise from natural differences between individuals or samples, measurement error, environmental changes, procedural inconsistencies, or random chance. Identifying and controlling sources of variability is essential for ensuring accurate, reliable, and reproducible results.
Example
In a clinical trial measuring blood pressure, sources of variability might include differences in patients’ baseline health conditions, the time of day blood pressure is measured, the type of blood pressure cuff used, and the technique of the healthcare professional taking the measurement. Recognizing and accounting for these factors helps ensure the results are valid and interpretable.