Multinomial Distribution					
				 
				
					
						
						 المؤلف:  
						Beyer, W. H.					
					
						
						 المصدر:  
						CRC Standard Mathematical Tables, 28th ed. Boca Raton, FL: CRC Press					
					
						
						 الجزء والصفحة:  
						...					
					
					
						
						18-4-2021
					
					
						
						2118					
				 
				
				
				
				
				
				
				
				
				
			 
			
			
				
				Multinomial Distribution
Let a set of random variates 
, 
, ..., 
 have a probability function
	
		
			  | 
			
			 (1) 
			 | 
		
	
where 
 are nonnegative integers such that
	
		
			  | 
			
			 (2) 
			 | 
		
	
and 
 are constants with 
 and
	
		
			  | 
			
			 (3) 
			 | 
		
	
Then the joint distribution of 
, ..., 
 is a multinomial distribution and 
 is given by the corresponding coefficient of the multinomial series
	
		
			  | 
			
			 (4) 
			 | 
		
	
In the words, if 
, 
, ..., 
 are mutually exclusive events with 
, ..., 
. Then the probability that 
 occurs 
 times, ..., 
 occurs 
 times is given by
	
		
			  | 
			
			 (5) 
			 | 
		
	
(Papoulis 1984, p. 75).
The mean and variance of 
 are
The covariance of 
 and 
 is
	
		
			  | 
			
			 (8) 
			 | 
		
	
REFERENCES:
Beyer, W. H. CRC Standard Mathematical Tables, 28th ed. Boca Raton, FL: CRC Press, p. 532, 1987.
Papoulis, A. Probability, Random Variables, and Stochastic Processes, 2nd ed. New York: McGraw-Hill, 1984.
				
				
					
					
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