Inter-laboratory comparison is a type of study in which multiple laboratories independently analyze the same samples to determine the level of agreement between their results. This type of research is often used to assess the reliability and reproducibility of analytical methods, as well as to identify sources of variability and areas for improvement in laboratory procedures. Inter-laboratory comparison studies can involve different types of samples, such as environmental samples, biological samples, or reference materials, and can be conducted on a local, national, or international scale. The results of inter-laboratory comparison studies can help ensure the accuracy and consistency of measurements and promote quality assurance in laboratory testing.