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1 . 下面给出四种说法:
①用相关指数
来刻画回归效果,
越小,说明模型的拟合效果越好;
②命题P:“
,
”的否定是¬P:“
,
”;
③设随机变量X服从正态分布
,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48fe8fe0f31762c1c6063bb9d413138e.png)
④回归直线一定过样本点的中心
.
其中正确的说法有___________ (请将你认为正确的说法的序号全部填写在横线上)
①用相关指数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c85067c53e936ef32da818efe04bdbb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c85067c53e936ef32da818efe04bdbb.png)
②命题P:“
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/02491f9709f00a1bc169278fbe01f576.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e3bf2891d3042a6f18860d2361eac0a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d96b743603ab1c10330622f16db78dbe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/371dfe9673b7df9d53e6d0dd6ad6f20f.png)
③设随机变量X服从正态分布
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37bbde2076bfa6dd859f7787e155ab8e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e73078757426543ae54d4aa30cf69390.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48fe8fe0f31762c1c6063bb9d413138e.png)
④回归直线一定过样本点的中心
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bda105ec292aac7ab1485bd5031783fb.png)
其中正确的说法有
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