n次测定结果的平均值的标准偏差S[img=~/QImg/2013-10-14-10-14-34/image023.jpg]与单次测量结果的标准偏差之间的关系是

A、[img=~/QImg/2013-10-14-10-14-34/image024.jpg]
B、[img=~/QImg/2013-10-14-10-14-34/image025.jpg]
C、[img=~/QImg/2013-10-14-10-14-34/image026.jpg]
D、[img=~/QImg/2013-10-14-10-14-34/image027.jpg]