问一道prep数学关于standard deviation的题目
A certain list of 100 data has an average (arithmetic mean) of 6 and a standard deviation of d, where d is positive. Which of the following pairs of data, when added to the list, must result in a list of 102 data with standard deviation less than d ?
(B) -6 and 0
(B) 0 and 0
(C) 0 and 6
(D) 0 and 12
(E) 6 and 6
请问这个题目怎么解...无概念中...
谢谢！
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