方差不用开根，标准差才要
by 123456zmy @ 2020-02-06 18:48:51
@[123456zmy](/user/44840) （初中大雾）谢谢！
by LeavingZ @ 2020-02-06 18:52:59
@[123456zmy](/user/44840) ~~我以后一定好好学数学~~
by LeavingZ @ 2020-02-06 18:57:12