52 lines
1.2 KiB
Python
52 lines
1.2 KiB
Python
# Sebastian Raschka 2014-2020
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# mlxtend Machine Learning Library Extensions
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#
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# Author: Sebastian Raschka <sebastianraschka.com>
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#
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# License: BSD 3 clause
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import numpy as np
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import scipy.stats
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def proportion_difference(proportion_1, proportion_2, n_1, n_2=None):
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"""
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Computes the test statistic and p-value for a difference of
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proportions test.
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Parameters
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-----------
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proportion_1 : float
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The first proportion
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proportion_2 : float
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The second proportion
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n_1 : int
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The sample size of the first test sample
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n_2 : int or None (default=None)
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The sample size of the second test sample.
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If `None`, `n_1`=`n_2`.
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Returns
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-----------
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z, p : float or None, float
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Returns the z-score and the p-value
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Examples
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-----------
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For usage examples, please see
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http://rasbt.github.io/mlxtend/user_guide/evaluate/proportion_difference/
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"""
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if n_2 is None:
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n_2 = n_1
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var_1 = proportion_1*(1. - proportion_1) / n_1
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var_2 = proportion_2*(1. - proportion_2) / n_2
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z = (proportion_1 - proportion_2) / np.sqrt(var_1 + var_2)
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p = scipy.stats.norm.cdf(z)
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return z, p
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