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Fonction epps_singleton_2samp - module scipy.stats

Signature de la fonction epps_singleton_2samp

def epps_singleton_2samp(x, y, t=(0.4, 0.8)) 

Description

epps_singleton_2samp.__doc__

Compute the Epps-Singleton (ES) test statistic.

    Test the null hypothesis that two samples have the same underlying
    probability distribution.

    Parameters
    ----------
    x, y : array-like
        The two samples of observations to be tested. Input must not have more
        than one dimension. Samples can have different lengths.
    t : array-like, optional
        The points (t1, ..., tn) where the empirical characteristic function is
        to be evaluated. It should be positive distinct numbers. The default
        value (0.4, 0.8) is proposed in [1]_. Input must not have more than
        one dimension.

    Returns
    -------
    statistic : float
        The test statistic.
    pvalue : float
        The associated p-value based on the asymptotic chi2-distribution.

    See Also
    --------
    ks_2samp, anderson_ksamp

    Notes
    -----
    Testing whether two samples are generated by the same underlying
    distribution is a classical question in statistics. A widely used test is
    the Kolmogorov-Smirnov (KS) test which relies on the empirical
    distribution function. Epps and Singleton introduce a test based on the
    empirical characteristic function in [1]_.

    One advantage of the ES test compared to the KS test is that is does
    not assume a continuous distribution. In [1]_, the authors conclude
    that the test also has a higher power than the KS test in many
    examples. They recommend the use of the ES test for discrete samples as
    well as continuous samples with at least 25 observations each, whereas
    `anderson_ksamp` is recommended for smaller sample sizes in the
    continuous case.

    The p-value is computed from the asymptotic distribution of the test
    statistic which follows a `chi2` distribution. If the sample size of both
    `x` and `y` is below 25, the small sample correction proposed in [1]_ is
    applied to the test statistic.

    The default values of `t` are determined in [1]_ by considering
    various distributions and finding good values that lead to a high power
    of the test in general. Table III in [1]_ gives the optimal values for
    the distributions tested in that study. The values of `t` are scaled by
    the semi-interquartile range in the implementation, see [1]_.

    References
    ----------
    .. [1] T. W. Epps and K. J. Singleton, "An omnibus test for the two-sample
       problem using the empirical characteristic function", Journal of
       Statistical Computation and Simulation 26, p. 177--203, 1986.

    .. [2] S. J. Goerg and J. Kaiser, "Nonparametric testing of distributions
       - the Epps-Singleton two-sample test using the empirical characteristic
       function", The Stata Journal 9(3), p. 454--465, 2009.