题目内容
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The standard deviation of four numbers a, b, c, d is M, then the standard deviation of which of the following MUST be M?
Indicate all such variations.
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Aa+1, b+1, c+1, d+1
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B2a, 2b, 2c, 2d
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Ca+1, b-1, c+1, d-1
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D$$√(a^2 )$$,$$ √(b^2 )$$, $$√(c^2 )$$, $$√(d^2 )$$
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