A、<img src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/47d36299-26e6-4856-ae0e-ccc8e9da18ef.jpg" width="127" height="29" />
B、<img src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/f2bc87a2-eee3-445c-8d75-3ef8f8244352.jpg" width="128" height="39" />
C、<img src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/c20442e9-0cd2-46f8-b727-ef50e94a47f3.jpg" width="127" height="40" />
D、<img src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/55f75303-9ecc-42f0-9bc4-c24d3cec9399.jpg" width="131" height="47" />
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和样本方差
，有：（ ）。[2010年初级真题]