title: how do i add variables with logistic distributions?
body: <p>i have X, Y, random logistic variables, how do I add them given the mean and scale for each?</p>
  
  <p><a href="http://en.wikipedia.org/wiki/Logistic_distribution" rel="nofollow noreferrer">Logistic distribution</a>.  i ran a simulation in python, but i cannot get it to be exact.</p>
  
  <p>i ran a simulation on getting a random number X, Y, and keep score on the value of X + Y.  then i did the same for getting a single random number with X + Y and test another scale based on the original scales, but i cannot fix the new scale to make them match</p>