From: mika.viljanen@iki.fifi.invalid   
      
   Tommy Stromhaug  wrote:   
   > Given tha classical alarm, earthquake, burglary, marycalls and   
   > johncalls. [...]   
   > It seems like P(A) is calculated as P(A,E,B)+P(A,-B,-E)+P(A,-B,E)+....   
   > just what i would have done except that i belived that i had to use   
   > P(J) and P(M) also.   
   > How is it that this is true ?   
   [...]   
   > arrows from B to A and from E to A   
   > arrows from A to J and from A to M   
      
   In this model J and M are dependent of A (as you can see in the directed   
   graph representation). So, calculating P(A|J,M)+...+P(A|~J,~M) would   
   provide no extra information (since the values of J and M already take   
   into account the value of A). HTH.   
      
   If someone else knows how to explain this better or finds something   
   wrong in my explanation, please feel free to correct me.   
      
   --   
   MJV   
      
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