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bpo-40290: Add zscore() to statistics.NormalDist. (GH-19547)

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Raymond Hettinger 2020-04-16 10:25:14 -07:00 • committed by GitHub
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11
Lib/statistics.py
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@ -999,6 +999,17 @@ class NormalDist:
x2 = (a - b) / dv
return 1.0 - (fabs(Y.cdf(x1) - X.cdf(x1)) + fabs(Y.cdf(x2) - X.cdf(x2)))
def zscore(self, x):
"""Compute the Standard Score. (x - mean) / stdev
Describes *x* in terms of the number of standard deviations
above or below the mean of the normal distribution.
"""
# https://www.statisticshowto.com/probability-and-statistics/z-score/
if not self._sigma:
raise StatisticsError('zscore() not defined when sigma is zero')
return (x - self._mu) / self._sigma
@property
def mean(self):
"Arithmetic mean of the normal distribution."