Interquartilic

Interquartilic is a neologism used in statistics and data analysis to describe concepts, measures, or methods related to the interval between the first and third quartiles of a data set. In its broad sense, interquartilic refers to anything that concerns the central portion of the distribution defined by Q1 (the 25th percentile) and Q3 (the 75th percentile). The term emphasizes the region that contains roughly 50% of the observations, rather than the tails.

Etymology: The word combines inter- meaning between, quartile from the quartile divisions of a rank-ordered data set, and the -ic suffix. It is not widely standardized and is primarily found in informal discourse, software documentation, or niche methodological papers.

Usage and interpretation: In practice, interquartilic discussions focus on robust summaries that are based on quartile boundaries, as opposed to mean-based measures. The interquartilic region is the interval [Q1, Q3], and the interquartilic dispersion is often equated with the interquartile range (IQR) equal to Q3 - Q1. Some authors use interquartilic methods to describe variability, central tendency, or density within this central band, and to compare distributions without assuming symmetry.

Relation to box plots and robust statistics: Box plots illustrate the interquartilic region via the box, with whiskers extending to capture tails. Interquartilic concepts appear in robust statistics when outliers are defined relative to quartile thresholds.

See also: interquartile range, quartile, box plot, robust statistics, percentile.

---