Exact confidence sets and goodness-of-fit methods for stable distributions
Usual
inference methods for stable distributions are typically based on limit
distributions. But asymptotic approximations can easily be unreliable in such
cases, for standard regularity conditions may not apply or may hold only
weakly. This paper proposes finite-sample tests and confidence sets for tail
thickness and asymmetry parameters (a and b ) of stable distributions. The
confidence sets are built by inverting exact goodness-of-fit tests for
hypotheses which assign specific values to these parameters. We propose
extensions of the Kolmogorov-Smirnov, Shapiro-Wilk and Filliben criteria, as
well as the quantile-based statistics proposed by McCulloch (1986) in order to
better capture tail behavior. The suggested criteria compare empirical
goodness-of-fit or quantile-based measures with their hypothesized values.
Since the distributions involved are quite complex and non-standard, the
relevant hypothetical measures are approximated by simulation, and p-values are
obtained using Monte Carlo (MC) test techniques. The properties of the proposed
procedures are investigated by simulation. In contrast with conventional
wisdom, we find reliable results with sample sizes as small as 25. The proposed
methodology is applied to daily electricity price data in the U.S. over the
period 2001-2006. The results show clearly that heavy kurtosis and asymmetry are
prevalent in these series.
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