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Frequency Distribution for List X
Number 1 2 3 5
Frequency 10 20 18 12
Frequency Distribution for List Y
Number 6 7 8 9
Frequency 24 17 10 9
List X and list Y each contain 60 numbers. Frequency distributions for each list are given above. The average (arithmetic mean) of the numbers in list X is 2.7, and the average of the numbers in list Y is 7.1. List Z contains 120 numbers: the 60 numbers in list X and the 60 numbers in list Y.
Quantity A Quantity B
The average of the 120numbers in list Z The median of the 120 numbers in list Z
A中，平均数肯定就是两组的平均数的和的一半，也就是(2.7+7.1)/2=4.9，因为两组的人数相同，而B中median就是(5+6)/2=5.5，所以就是B了。