设总体 <img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/2b29d93a908048d1b014085032302fae.png?x-oss-process=image/sharpen,200"/> 服从 <img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/900faef0bddf4e81b55a92ec3debb638.png?x-oss-process=image/sharpen,200"/> 分布，<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/ec0b671b70664f6f8e054ee6dbb90b6f.png?x-oss-process=image/sharpen,200"/> 为样本，<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/6e47f110681b4abb9fea991266528c5f.png?x-oss-process=image/sharpen,200"/> 为样本均值，则以下结论中错误的是（）。