stanine

noun

sta·​nine ˈstā-ˌnīn 

: any of the nine classes into which a set of normalized standard scores arranged according to rank in educational testing are divided, which include the bottom 4 percent and the top 4 percent of the scores in the first and ninth classes and the middle 20 percent in the fifth, and which have a standard deviation of 2 and a mean of 5

Word History

Etymology

standard (score) + nine

First Known Use

1944, in the meaning defined above