Kendall rank correlation coefficient

Ever wonder how to measure if two rankings are similar?

Imagine you're comparing the rankings of your favorite books from two different lists. You want to know how closely the rankings match.

Think of it as counting how many times two lists agree on the order of items. The closer the agreement, the stronger the connection between the lists.

Example

List A ranks "Book X" as 1st, "Book Y" as 2nd, and "Book Z" as 3rd. List B ranks "Book Y" as 1st, "Book X" as 2nd, and "Book Z" as 3rd. They agree on the order of "Book Y" and "Book Z", showing a strong connection.

Remember this

Spearman's rank correlation coefficient (ρ) quantifies the degree to which two rankings agree.

Text adapted from Wikipedia, licensed under CC BY-SA 4.0.

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