text: def diff_of_means(data_1, data_2):
      """Difference in means of two arrays."""
  
      # The difference of means of data_1, data_2: diff
      diff = np.mean(data_1) - np.mean(data_2)
  
      return diff
  
  # Compute difference of mean impact force from experiment: empirical_diff_means
  empirical_diff_means = diff_of_means(force_a, force_b)
  
  # Draw 10,000 permutation replicates: perm_replicates
  perm_replicates = draw_perm_reps(force_a, force_b,
                                   diff_of_means, size=10000)
  
  # Compute p-value: p
  p = np.sum(perm_replicates >= empirical_diff_means) / len(perm_replicates)
  
  # Print the result
  print('p-value =', p)
  