Ad-Plot and Ud-Plot for Visualizing Distributional Properties
and Normality
Description
The empirical cumulative average deviation function introduced by the author is utilized to
develop both Ad- and Ud-plots. The Ad-plot can identify symmetry, skewness, and outliers of the
data distribution, including anomalies. The Ud-plot created by slightly modifying Ad-plot is
exceptional in assessing normality, outperforming normal QQ-plot, normal PP-plot, and their
derivations. The d-value that quantifies the degree of proximity between the Ud-plot and the graph
of the estimated normal density function helps guide to make decisions on confirmation of
normality. Full description of this methodology can be found in the article by Wijesuriya (2025)
.