title: How to calculate expected relative frequency from observed data in python
body: <p>I have a data sets with mean = 40, sd = 5 with equal class interval of 20 starting with 30, so the first frequency class is (30 -50). I have calculate the expected relative cumulative frequency (in normal distribution) for first class by using the code below</p>
  
  <pre><code>scipy.stats.norm.cdf((50-mean)/sd)-scipy.stats.norm.cdf((30-mean)/sd)
  </code></pre>
  
  <p>then how can I calculate the expected value for up to 10 classes by defining the function so that the expected value for second class will be</p>
  
  <pre><code>scipy.stats.norm.cdf((70-mean)/sd)-scipy.stats.norm.cdf((50-mean)/sd)
  </code></pre>
  
  <p>Any help on this problem is highly appriciated.</p>