Statistics Papers

Document Type

Journal Article

Date of this Version

2017

Publication Source

The American Statistician

Volume

71

Issue

2

Start Page

145

Last Page

147

DOI

10.1080/00031305.2016.1200488

Abstract

A normal quantile-quantile (QQ) plot is an important diagnostic for checking the assumption of normality. Though useful, these plots confuse students in my introductory statistics classes. A water-filling analogy, however, intuitively conveys the underlying concept. This analogy characterizes a QQ plot as a parametric plot of the water levels in two gradually filling vases. Each vase takes its shape from a probability distribution or sample. If the vases share a common shape, then the water levels match throughout the filling, and the QQ plot traces a diagonal line. An R package qqvases provides an interactive animation of this process and is suitable for classroom use.

Keywords

Education, diagnostic, simulation

Embargo Date

6-6-2018

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Date Posted: 27 November 2017

This document has been peer reviewed.