important points in 7.5.4:
		
	
	
	
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								understanding discrete vs. continuous
							
						
					
				
				
 
 
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								for a continuous random variable, probabilities of an interval of values are represented by areas (that are sectioned off by vertical slices).
							
						
					
				
				
 
 
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								for a continuous random variable the probability that x=(
									any specific value) = 0.  for a continuous variable there are an infinite number of possible values the variable can have.  even if you think of each one as equally likely (as in a uniform distribution), the probability of any one particular value is 1/(infinity) which is 0.
							
						
					
				
				
 
 
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								"
									
										expected value
									" is a term that means the mean (average)
							
						
					
				
				
 
 
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								the mean (“expected value”) is the "balance point" of the area