statsmodels.stats.weightstats.CompareMeans.zconfint_diff

CompareMeans.zconfint_diff(alpha=0.05, alternative='two-sided', usevar='pooled')

confidence interval for the difference in means

Parameters:

• alpha (float) – significance level for the confidence interval, coverage is 1-alpha
• alternative (string) –

  This specifies the alternative hypothesis for the test that corresponds to the confidence interval. The alternative hypothesis, H1, has to be one of the following :

  ’two-sided’: H1: difference in means not equal to value (default) ‘larger’ : H1: difference in means larger than value ‘smaller’ : H1: difference in means smaller than value

• usevar (string, 'pooled' or 'unequal') – If pooled, then the standard deviation of the samples is assumed to be the same. If unequal, then Welsh ttest with Satterthwait degrees of freedom is used

Returns:

lower, upper – lower and upper limits of the confidence interval

Return type:

floats

Notes

The result is independent of the user specified ddof.