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		| Paper: | 
		Discussion on Romanishin and Tegler Paper | 
	 
	
		| Volume: | 
		371, Statistical Challenges in Modern Astronomy IV | 
	 
	
		| Page: | 
		220 | 
	 
	
		| Authors: | 
		Zhu, Z. | 
	 
	
	
		| Abstract: | 
		We give a brief description of the tip test and caution its misuse when the goal is to determine whether the observed data are consisted of more than one class of objects. A more appropriate approach for this purpose based on finite mixture models and model-based clustering is introduced as an alternative. This approach is applied to the color distribution of the Plutinos, which indicates that the color distribution may be a mixture of two normal distribution with equal variance. | 
	 
	
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