Published online by Cambridge University Press: 01 January 2025
The properties of nonmetric multidimensional scaling (NMDS) are explored by specifying statistical models, proving statistical consistency, and developing hypothesis testing procedures. Statistical models with errors in the dependent and independent variables are described for quantitative and qualitative data. For these models, statistical consistency often depends crucially upon how error enters the model and how data are collected and summarized (e.g., by means, medians, or rank statistics). A maximum likelihood estimator for NMDS is developed, and its relationship to the standard Shepard-Kruskal estimation method is described. This maximum likelihood framework is used to develop a method for testing the overall fit of the model.
In the preparation of this manuscript Chris Achen helped in innumerable ways by providing a judicious combination of criticism and encouragement. Professors J. O. Ramsay and Roger Shepard generously took the time to respond to an earlier version. I take responsibility for all remaining errors.