单项选择题
A.2.65 B.2.44 C.1.96 D.1.645
A.越窄 B.越宽 C.不变,因为均值不变 D.越接近1.96
A.0.4664 B.0.9328 C.0.9664 D.0.0336
A.0.4664 B.0.9328 C.0.0336 D.0.0672
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