某公司为确定下一年度投入某种产品的宣传费,需了解年宣传费
\(x\)\((\)单位:千元\()\)对年销售量
\(y\)\((\)单位:\(t)\)和年利润
\(z\)\((\)单位:千元\()\)的影响,对近\(8\)年的年宣传费
\(x\)\({\,\!}_{i}\)和年销售量
\(y\)\({\,\!}_{i}( \)
\(i\)\(=1\),\(2\),\(…\),\(8)\)数据作了初步处理,得到下面的散点图及一些统计量的值.
![](https://www.ebk.net.cn/tikuimages/2/2016/600/shoutiniao23/fa5569a9f9a823a63502875d05a67178.png)
![](https://www.ebk.net.cn/tikuimages/2/2016/600/shoutiniao94/9920b747c6012e28164d63416ecc141f.png)
表中\(w_{i}\)\(=\)
,
\(=\)![](https://www.ebk.net.cn/tikuimages/2/2016/600/shoutiniao54/0c1abea95fcbf8b60fabacf8ee9f3d6e.png)
\({\,\!}_{i}\).
\((1)\)根据散点图判断,\(y\)\(=\)\(a\)\(+\)\(bx\)与\(y\)\(=\)\(c\)\(+\)\(d\)
哪一个适宜作为年销售量\(y\)关于年宣传费\(x\)的回归方程类型?\((\)给出判断即可,不必说明理由\()\)
\((2)\)根据\((1)\)的判断结果及表中数据,建立\(y\)关于\(x\)的回归方程;
\((3)\)已知这种产品的年利润\(z\)与\(x\),\(y\)的关系为\(z\)\(=0.2\)\(y\)\(-\)\(x\)\(.\)根据\((2)\)的结果回答下列问题:
\(①\)年宣传费\(x\)\(=49\)时,年销售量及年利润的预报值是多少?
\(②\)年宣传费\(x\)为何值时,年利润的预报值最大?
附:对于一组数据\((\)\(u\)\({\,\!}_{1}\),\(v\)\({\,\!}_{1})\),\((\)\(u\)\({\,\!}_{2}\),\(v\)\({\,\!}_{2})\),\(…\),\((\)\(u\)\({\,\!}_{n}\),\(v_{n}\)\()\),其回归直线\(v\)\(=\)\(α\)\(+\)\(βu\)的斜率和截距的最小二乘估计分别为:
\(=\)
,
\(=\)
\(-\)![](https://www.ebk.net.cn/tikuimages/2/2016/600/shoutiniao88/b8171009424c186dd3c8f1091230d6d6.png)
.