dask.array.stats.ttest_1samp(a, popmean, axis=0, nan_policy='propagate')[source]

Calculate the T-test for the mean of ONE group of scores.

This docstring was copied from scipy.stats.ttest_1samp.

Some inconsistencies with the Dask version may exist.

This is a two-sided test for the null hypothesis that the expected value (mean) of a sample of independent observations a is equal to the given population mean, popmean.


Sample observation.

popmeanfloat or array_like

Expected value in null hypothesis. If array_like, then it must have the same shape as a excluding the axis dimension.

axisint or None, optional

Axis along which to compute test; default is 0. If None, compute over the whole array a.

nan_policy{‘propagate’, ‘raise’, ‘omit’}, optional

Defines how to handle when input contains nan. The following options are available (default is ‘propagate’):

  • ‘propagate’: returns nan

  • ‘raise’: throws an error

  • ‘omit’: performs the calculations ignoring nan values

alternative{‘two-sided’, ‘less’, ‘greater’}, optional (Not supported in Dask)

Defines the alternative hypothesis. The following options are available (default is ‘two-sided’):

  • ‘two-sided’

  • ‘less’: one-sided

  • ‘greater’: one-sided

New in version 1.6.0.

statisticfloat or array


pvaluefloat or array

Two-sided p-value.


>>> from scipy import stats  
>>> rng = np.random.default_rng()  
>>> rvs = stats.norm.rvs(loc=5, scale=10, size=(50, 2), random_state=rng)  

Test if mean of random sample is equal to true mean, and different mean. We reject the null hypothesis in the second case and don’t reject it in the first case.

>>> stats.ttest_1samp(rvs, 5.0)  
Ttest_1sampResult(statistic=array([-2.09794637, -1.75977004]), pvalue=array([0.04108952, 0.08468867]))
>>> stats.ttest_1samp(rvs, 0.0)  
Ttest_1sampResult(statistic=array([1.64495065, 1.62095307]), pvalue=array([0.10638103, 0.11144602]))

Examples using axis and non-scalar dimension for population mean.

>>> result = stats.ttest_1samp(rvs, [5.0, 0.0])  
>>> result.statistic  
array([-2.09794637,  1.62095307])
>>> result.pvalue  
array([0.04108952, 0.11144602])
>>> result = stats.ttest_1samp(rvs.T, [5.0, 0.0], axis=1)  
>>> result.statistic  
array([-2.09794637,  1.62095307])
>>> result.pvalue  
array([0.04108952, 0.11144602])
>>> result = stats.ttest_1samp(rvs, [[5.0], [0.0]])  
>>> result.statistic  
array([[-2.09794637, -1.75977004],
       [ 1.64495065,  1.62095307]])
>>> result.pvalue  
array([[0.04108952, 0.08468867],
       [0.10638103, 0.11144602]])