Spearman's rank correlation coefficient
Sometimes, when ranking data, there are two or more numbers that are the same. When this happens in , we take the mean or average of the ranks that are the same. These are called tied ranks. To do this, we rank the tied numbers as if they were not tied. Then, we add up all the ranks that they would have, and divide it by how many there are.  For example, say we were ranking how well different people did in a spelling test.