paired sign test in Python
from scipy.stats import binomtest, shapiro import numpy as np alpha = 0.05 Example 1
before = np.array([120, 130, 135, 140, 135, 150, 140, 130, 145, 138]) after = np.array([118, 125, 130, 135, 133, 152, 137, 132, 146, 139]) differences = before - after print(differences) 
positive_diffs = np.sum(differences > 0) negative_diffs = np.sum(differences < 0) test_statistic = min(positive_diffs, negative_diffs) print(test_statistic) 
n = positive_diffs + negative_diffs results = binomtest(test_statistic, n, p=0.5, alternative='two-sided') p_value = results.pvalue print(p_value) 
if p_value < alpha: print("The median of the differences is not zero (there is a difference).") else: print("The median of the differences between the paired observations is zero (no difference)..") 
Example 2 #one tail #zero value #shapiro #ordinal data
before = np.array([3, 4, 2, 4, 3, 4, 5, 3, 4, 2]) after = np.array([2, 4, 3, 5, 3, 5, 5, 4, 5, 3]) differences = before - after print(differences) 
shapiro_stat, shapiro_p_value = shapiro(differences) print(shapiro_p_value) 
positive_diffs = np.sum(differences > 0) negative_diffs = np.sum(differences < 0) test_statistic = min(positive_diffs, negative_diffs) print(test_statistic) 
n = positive_diffs + negative_diffs print(n) 
results = binomtest(test_statistic, n=n, p=0.5, alternative='less') p_value = results.pvalue print(p_value) 
if p_value < alpha: print("The median of the differences is not zero (there is a difference which is less).") else: print("The median of the differences between the paired observations is zero (no difference)..") 
Example statsmodel
import statsmodels from statsmodels.stats.descriptivestats import sign_test before = np.array([120, 130, 135, 140, 135, 150, 140, 130, 145, 138]) after = np.array([118, 125, 130, 135, 133, 152, 137, 132, 146, 139]) sign_test(before, after) 
