What is Kappa statistic used for in research?

The Kappa statistic is used to measure the agreement between two raters who are evaluating categorical data. This statistic provides a way to quantify the level of agreement beyond what would be expected by chance. It is particularly useful in research settings where subjective judgments are made, such as in clinical assessments or diagnostic tests, to determine the consistency of ratings by different observers. By calculating Kappa, researchers can assess not only the extent of agreement but also how substantial that agreement is.

This statistic is especially important in fields like psychology, medicine, and social sciences, where understanding the level of concordance between different evaluators can impact the validity of the findings and their implications for practice.