kurtosistest#
- scipy.stats.kurtosistest(a, axis=0, nan_policy='propagate', alternative='two-sided', *, keepdims=False)[source]#
Test whether a dataset has normal kurtosis.
This function tests the null hypothesis that the kurtosis of the population from which the sample was drawn is that of the normal distribution.
- Parameters:
- aarray
Array of the sample data. Must contain at least five observations.
- axisint or None, default: 0
If an int, the axis of the input along which to compute the statistic. The statistic of each axis-slice (e.g. row) of the input will appear in a corresponding element of the output. If
None
, the input will be raveled before computing the statistic.- nan_policy{‘propagate’, ‘omit’, ‘raise’}
Defines how to handle input NaNs.
propagate
: if a NaN is present in the axis slice (e.g. row) along which the statistic is computed, the corresponding entry of the output will be NaN.omit
: NaNs will be omitted when performing the calculation. If insufficient data remains in the axis slice along which the statistic is computed, the corresponding entry of the output will be NaN.raise
: if a NaN is present, aValueError
will be raised.
- alternative{‘two-sided’, ‘less’, ‘greater’}, optional
Defines the alternative hypothesis. The following options are available (default is ‘two-sided’):
‘two-sided’: the kurtosis of the distribution underlying the sample is different from that of the normal distribution
‘less’: the kurtosis of the distribution underlying the sample is less than that of the normal distribution
‘greater’: the kurtosis of the distribution underlying the sample is greater than that of the normal distribution
Added in version 1.7.0.
- keepdimsbool, default: False
If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.
- Returns:
- statisticfloat
The computed z-score for this test.
- pvaluefloat
The p-value for the hypothesis test.
See also
- Kurtosis test
Extended example
Notes
Valid only for n>20. This function uses the method described in [1].
Beginning in SciPy 1.9,
np.matrix
inputs (not recommended for new code) are converted tonp.ndarray
before the calculation is performed. In this case, the output will be a scalar ornp.ndarray
of appropriate shape rather than a 2Dnp.matrix
. Similarly, while masked elements of masked arrays are ignored, the output will be a scalar ornp.ndarray
rather than a masked array withmask=False
.References
[1]F. J. Anscombe, W. J. Glynn, “Distribution of the kurtosis statistic b2 for normal samples”, Biometrika, vol. 70, pp. 227-234, 1983.
Examples
>>> import numpy as np >>> from scipy.stats import kurtosistest >>> kurtosistest(list(range(20))) KurtosistestResult(statistic=-1.7058104152122062, pvalue=0.08804338332528348) >>> kurtosistest(list(range(20)), alternative='less') KurtosistestResult(statistic=-1.7058104152122062, pvalue=0.04402169166264174) >>> kurtosistest(list(range(20)), alternative='greater') KurtosistestResult(statistic=-1.7058104152122062, pvalue=0.9559783083373583) >>> rng = np.random.default_rng() >>> s = rng.normal(0, 1, 1000) >>> kurtosistest(s) KurtosistestResult(statistic=-1.475047944490622, pvalue=0.14019965402996987)
For a more detailed example, see Kurtosis test.