rank-difference correlation vs statistics

rank-difference correlation and statistics both are nouns.

Word	Noun	Adjective	Verb	Adverb
rank-difference correlation	Yes	No	No	No
statistics	Yes	No	No	No

rank-difference correlation (noun)	statistics (noun)
the most commonly used method of computing a correlation coefficient between the ranks of scores on two variables	a branch of applied mathematics concerned with the collection and interpretation of quantitative data and the use of probability theory to estimate population parameters