statsmodels.stats.rates.power_poisson_diff_2indep

statsmodels.stats.rates.power_poisson_diff_2indep(rate1, rate2, nobs1, nobs_ratio=1, alpha=0.05, value=0, method_var='score', alternative='two-sided', return_results=True)

Power of ztest for the difference between two independent poisson rates

Parameters:

rate1float

Poisson rate for the first sample, treatment group, under the alternative hypothesis.

rate2float

Poisson rate for the second sample, reference group, under the alternative hypothesis.

nobs1float or array_like

Number of observations in sample 1.

nobs_ratiofloat, optional

Sample size ratio, nobs2 = nobs_ratio * nobs1.

alphafloat or array_like in interval (0,1), optional

Significance level, e.g., 0.05, is the probability of a type I error, that is wrong rejections if the Null Hypothesis is true.

valuefloat, optional

Difference between rates 1 and 2 under the null hypothesis.

method_var{“score”, “alt”}, optional

The variance of the test statistic for the null hypothesis given the rates under the alternative, can be either equal to the rates under the alternative method_var="alt", or estimated under the constrained of the null hypothesis, method_var="score".

alternative{‘two-sided’, ‘larger’, ‘smaller’}, optional

Alternative hypothesis whether the power is calculated for a two-sided (default) or one sided test. The one-sided test can be either ‘larger’, ‘smaller’.

return_resultsbool, optional

If true, then a results instance with extra information is returned, otherwise only the computed power is returned.

Returns:

PowerDiffResult or float

If return_results is False, then only the power is returned as a float. If return_results is True (default), then a PowerDiffResult result object is returned; it behaves like the scalar power in numeric comparisons (e.g., assert_allclose), while also exposing std_null, std_alt and other attributes.

References

[1]

Stucke, Kathrin, and Meinhard Kieser. 2013. “Sample Size Calculations for Noninferiority Trials with Poisson Distributed Count Data.” Biometrical Journal 55 (2): 203-16. https://doi.org/10.1002/bimj.201200142.

[2]

PASS manual chapter 436