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

confidence interval for the difference in means


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


lower, upper : floats

lower and upper limits of the confidence interval


The result is independent of the user specified ddof.