title: The result of mann-whitney u test in Jupyter notebook couldn't be reproduced
body: <p>The result of mann-whitney u test in Jupyter notebook couldn't be reproduced.</p>
  
  <p>First, we did mann-whitney u test for test dataset.
  <a href="https://i.stack.imgur.com/X8nnY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X8nnY.png" alt="enter image description here"></a></p>
  
  <p>Second, we did mann-whitney u test for my dataset. I have to apologize that my dataset cannot be attached because that is very big and confidential data.
  <a href="https://i.stack.imgur.com/Njml5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Njml5.png" alt="enter image description here"></a></p>
  
  <p>Then, we did mann-whitney u test for test dataset again and got the error messege.
  <a href="https://i.stack.imgur.com/jykb5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jykb5.png" alt="enter image description here"></a></p>
  
  <p>Did you know this phenomenon?
  What can be the reason for this phenomenon?</p>
  
  <p>MacOS 10.14.5
  python 3.7.2
  jupyter notebook 4.4.0</p>
  
  <pre><code>import numpy as np
  from scipy
  
  np.random.seed(12345678)  #fix random seed to get the same result
  n1 = 200  # size of first sample
  n2 = 300  # size of second sample
  rvs1 = stats.norm.rvs(size=n1, loc=0., scale=1)
  rvs2 = stats.norm.rvs(size=n2, loc=0.5, scale=1.5)
  print(stats.mannwhitneyu(rvs1, rvs2))
  print(type(rvs1))
  print(len(rvs1))
  print(len(rvs2))
  print(stats.ks_2samp(rvs1, rvs2))
  
  alive= np.loadtxt('alive.csv', delimiter=',', dtype='int64')
  expired= np.loadtxt('expired.csv', delimiter=',', dtype='int64')
  
  print(stats.mannwhitneyu(alive, expired))
  print("p-value")
  print(np.round(stats.mannwhitneyu(alive, expired).pvalue, decimals=4))
  print("statistics")
  print(len(alive))
  len_alive = len(alive)
  print(len(expired))
  len_expired = len(expired)
  stats = stats.mannwhitneyu(alive, expired).statistic
  ps = stats/(len_alive * len_expired)
  print(ps)
  </code></pre>