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# scipy.stats.shapiro

`scipy.stats.``shapiro`(x, a=None, reta=False)

  Perform the Shapiro-Wilk test for normality.

  The Shapiro-Wilk test tests the null hypothesis that the data was drawn from a normal distribution.

  Parameters:

  x : array_like

  > Array of sample data.

  a : array_like, optional

  > Array of internal parameters used in the calculation. If these are not given, they will be computed internally. If x has length n, then a must have length n/2.

  reta : bool, optional

  > Whether or not to return the internally computed a values. The default is False.

  Returns:

  W : float

  > The test statistic.

  p-value : float

  > The p-value for the hypothesis test.

  a : array_like, optional

  > If reta is True, then these are the internally computed “a” values that may be passed into this function on future calls.

  See also

  `anderson`
    The Anderson-Darling test for normality
  `kstest`
    The Kolmogorov-Smirnov test for goodness of fit.

  Notes

  The algorithm used is described in [R607] but censoring parameters as described are not implemented. For N > 5000 the W test statistic is accurate but the p-value may not be.

  The chance of rejecting the null hypothesis when it is true is close to 5% regardless of sample size.

  References

  [R604] | http://www.itl.nist.gov/div898/handbook/prc/section2/prc213.htm

  [R605] | Shapiro, S. S. & Wilk, M.B (1965). An analysis of variance test for normality (complete samples), Biometrika, Vol. 52, pp. 591-611.

  [R606] | Razali, N. M. & Wah, Y. B. (2011) Power comparisons of Shapiro-Wilk, Kolmogorov-Smirnov, Lilliefors and Anderson-Darling tests, Journal of Statistical Modeling and Analytics, Vol. 2, pp. 21-33.

  [R607] | (1, 2) ALGORITHM AS R94 APPL. STATIST. (1995) VOL. 44, NO. 4.

  Examples

      >>> from scipy import stats
      >>> np.random.seed(12345678)
      >>> x = stats.norm.rvs(loc=5, scale=3, size=100)
      >>> stats.shapiro(x)
      (0.9772805571556091, 0.08144091814756393)