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-  We estimated  
  by
 
 , where  
  is the total number of training
instances where  
  and  
  is the number of these
where  
 . -  Good estimate except when  
  gets too small (e.g., goes to zero). -  m-estimate of probability:  
 ,
where  
  is the prior estimate of the probability and  
  is the
equivalent sample size -  Can be interpreted as augmenting the  
  actual observations
by an additional  
  virtual samples distributed according to  
  
 
Patricia Riddle 
Fri May 15 13:00:36 NZST 1998