Fleiss' Kappa is a statistical measure used to assess the reliability of agreement between multiple raters or judges. It evaluates how much the ratings given by different observers agree beyond what would be expected by chance. The value of Fleiss' Kappa ranges from -1 to 1, where 1 indicates perfect agreement, 0 indicates no agreement beyond chance, and negative values suggest disagreement. This measure is particularly useful in fields like psychology, medicine, and social sciences, where subjective assessments are common. By quantifying the level of agreement, researchers can better understand the consistency of their data and improve the reliability of their findings.