Adjusted Rand index

The Adjusted Rand Index (ARI) is a statistical measure used to evaluate the similarity between two different ways of grouping data, such as clustering results. It considers all pairs of data points to see if they are grouped together or separately in both methods. The ARI adjusts for chance, meaning it accounts for the likelihood that some agreements might occur just by random chance. Values range from -1 to 1; a value of 1 indicates perfect agreement, 0 means no better than random chance, and negative values denote worse than random grouping. It’s a valuable tool in data analysis for assessing clustering quality.