Accurate and Efficient Approximation of the Null Distribution of Rao's Spacing Test

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Autori principali: Kinoshita, Yoshiki, Shinozaki, Aya, Kamakura, Toshinari
Natura: Preprint
Pubblicazione: 2026
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author Kinoshita, Yoshiki
Shinozaki, Aya
Kamakura, Toshinari
author_facet Kinoshita, Yoshiki
Shinozaki, Aya
Kamakura, Toshinari
contents Rao's spacing test is a widely used nonparametric method for assessing uniformity on the circle. However, its broader applicability in practical settings has been limited because the null distribution is not easily calculated. As a result, practitioners have traditionally depended on pre-tabulated critical values computed for a limited set of sample sizes, which restricts the flexibility and generality of the method. In this paper, we address this limitation by recursively computing higher-order moments of the Rao's spacing test statistic and employing the Gram-Charlier expansion to derive an accurate approximation to its null distribution. This approach allows for the efficient and direct computation of p-values for arbitrary sample sizes, thereby eliminating the dependency on existing critical value tables. Moreover, we confirm that our method remains accurate and effective even for large sample sizes that are not represented in current tables, thus overcoming a significant practical limitation. Comparative evaluations with published critical values and saddlepoint approximations demonstrate that our method achieves a high degree of accuracy across a wide range of sample sizes. These findings greatly improve the practicality and usability of Rao's spacing test in both theoretical investigations and applied statistical analyses.
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id arxiv_https___arxiv_org_abs_2602_04318
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Accurate and Efficient Approximation of the Null Distribution of Rao's Spacing Test
Kinoshita, Yoshiki
Shinozaki, Aya
Kamakura, Toshinari
Methodology
Statistics Theory
Rao's spacing test is a widely used nonparametric method for assessing uniformity on the circle. However, its broader applicability in practical settings has been limited because the null distribution is not easily calculated. As a result, practitioners have traditionally depended on pre-tabulated critical values computed for a limited set of sample sizes, which restricts the flexibility and generality of the method. In this paper, we address this limitation by recursively computing higher-order moments of the Rao's spacing test statistic and employing the Gram-Charlier expansion to derive an accurate approximation to its null distribution. This approach allows for the efficient and direct computation of p-values for arbitrary sample sizes, thereby eliminating the dependency on existing critical value tables. Moreover, we confirm that our method remains accurate and effective even for large sample sizes that are not represented in current tables, thus overcoming a significant practical limitation. Comparative evaluations with published critical values and saddlepoint approximations demonstrate that our method achieves a high degree of accuracy across a wide range of sample sizes. These findings greatly improve the practicality and usability of Rao's spacing test in both theoretical investigations and applied statistical analyses.
title Accurate and Efficient Approximation of the Null Distribution of Rao's Spacing Test
topic Methodology
Statistics Theory
url https://arxiv.org/abs/2602.04318