Confidence Intervals After Variance Stabilization May Go Head-to-Head with Exact Confidence Intervals: A New Class of Illustrations

• Published in: Bulletin - Calcutta Statistical Association Vol. 73; no. 2; pp. 79 - 93
• Main Author: Mukhopadhyay, Nitis
• Format: Journal Article
• Language: English
• Published: New Delhi, India SAGE Publications 01.11.2021
• Subjects: Confidence intervals; Pedagogy; square-root transformation; Arcsine transformation; Fisher's z-transformation; variance stabilizing transformation (VST); Comparing VST vs exact
• ISSN: 0008-0683; 2456-6462
• DOI: 10.1177/00080683211051170

We begin with an overview on variance stabilizing transformations (VST) along with three classical examples for completeness: the arcsine, square-root and Fisher's z-transformations (Examples 1–3). Then, we construct three new examples (Examples 4–6) of VST-based and central limit theorem (CLT)’based large-sample confidence interval methodologies. These are special examples in the sense that in each situation, we also have an exact confidence interval procedure for the parameter of interest. Tables 1–3 obtained exclusively under Examples 4–6 via exact calculations show that the VST-based (a) large-sample confidence interval methodology wins over the CLT-based large-sample confidence interval methodology, (b) confidence intervals’ exact coverage probabilities are better than or nearly same as those associated with the exact confidence intervals and (c) intervals are never wider (in the log-scale) than the CLT-based intervals across the board. A possibility of such a surprising behaviour of the VST-based confidence intervals over the exact intervals was not on our radar when we began this investigation. Indeed the VST-based inference methodologies may do extremely well, much more so than the existing literature reveals as evidenced by the new Examples 4–6. AMS subject classifications: 62E20; 62F25; 62F12