1.已知样本10, 8, 6, 10, 8,13,11,10,12,7,8,9,12,9, 11,12,9,10,11,11, 那么频率为0.2范围的是 ( )
A. 5.5~7.5 B. 7.5~9.5 C. 9.5~11.5 D. 11.5~13.5
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