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View Full Version : as to "arithmetic mean" and "weighted average"



seeker
03-12-2003, 01:18 AM
Following is REQUENCY DISTRIBUTION of 3 groups of data, among which the number within brackets means frequency of that data antecedes it(un-bracketed)£º
A. 1£¨6£©£¬2£¨4£©£¬3£¨1£©£¬4£¨4£©£¬5£¨6£©
B. 1£¨1£©£¬2£¨4£©£¬3£¨6£©£¬4£¨4£©£¬5£¨1£©
C. 1£¨1£©£¬2£¨2£©£¬3£¨3£©£¬4£¨4£©£¬5£¨5£©
Question: The MEAN of which group equals with its AVERAGE
Key£ºB

However, I think A is also an answer, see:
For group B
mean-arithmetic mean: ª¤£¨1+2+3+4+5£©/ 5 = 3
average-weighted average: (1*1+2*4+...5*1)/(1+4+6+4+1)=48/16=3

For group A
mean-arithmetic mean:ª¤£¨1+2+3+4+5£©/ 5 = 3
average-weighted average: (1*6+2*4+...5*6)/(6+4+1+4+6)=63/21=3


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