18. 某湿地公园经过近十年的规划和治理,生态系统得到很大改善,野生动物数量有所增加.为调查该地区某种野生动物的数量,将其分成面积相近的300个地块,并设计两种抽样方案,方案一:在该地区应用简单随机抽样的方法抽取30个作为样本区;依据抽样数据计算得到相应的相关系数
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3Er%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E0.81%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
;方案二:在该地区应用分层抽样的方法抽取30个作为样本区,调查得到样本数据
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmrow%3E%3Cmo%3E%28%3C%2Fmo%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3Cmo%3E%2C%3C%2Fmo%3E%3Cmsub%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3C%2Fmrow%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmrow%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
(
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3Ei%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,2,…,30),其中
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
和
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
分别表示第i个样区的植物覆盖面积(单位:公顷)和这种野生动物的数量,并计算得
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmstyle+displaystyle%3D%22true%22%3E%3Cmunderover%3E%3Cmo%3E%E2%88%91%3C%2Fmo%3E%3Cmrow%3E%3Cmi%3Ei%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E30%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmunderover%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3C%2Fmrow%3E%3C%2Fmstyle%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E60%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmstyle+displaystyle%3D%22true%22%3E%3Cmunderover%3E%3Cmo%3E%E2%88%91%3C%2Fmo%3E%3Cmrow%3E%3Cmi%3Ei%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E30%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmunderover%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3C%2Fmrow%3E%3C%2Fmstyle%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1200%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmstyle+displaystyle%3D%22true%22%3E%3Cmunderover%3E%3Cmo%3E%E2%88%91%3C%2Fmo%3E%3Cmrow%3E%3Cmi%3Ei%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E30%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmunderover%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmrow%3E%3Cmo%3E%28%3C%2Fmo%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmover+accent%3D%22true%22%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmo+stretchy%3D%22true%22%3E%C2%AF%3C%2Fmo%3E%3C%2Fmover%3E%3C%2Fmrow%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmrow%3E%3C%2Fmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmstyle%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E90%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmstyle+displaystyle%3D%22true%22%3E%3Cmunderover%3E%3Cmo%3E%E2%88%91%3C%2Fmo%3E%3Cmrow%3E%3Cmi%3Ei%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E30%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmunderover%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmrow%3E%3Cmo%3E%28%3C%2Fmo%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmover+accent%3D%22true%22%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmo+stretchy%3D%22true%22%3E%C2%AF%3C%2Fmo%3E%3C%2Fmover%3E%3C%2Fmrow%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmrow%3E%3C%2Fmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmstyle%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E8000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,
![](http://math.21cnjy.com/mml2svg?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmstyle+displaystyle%3D%22true%22%3E%3Cmunderover%3E%3Cmo%3E%E2%88%91%3C%2Fmo%3E%3Cmrow%3E%3Cmi%3Ei%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E30%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmunderover%3E%3Cmrow%3E%3Cmrow%3E%3Cmo%3E%28%3C%2Fmo%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmover+accent%3D%22true%22%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmo+stretchy%3D%22true%22%3E%C2%AF%3C%2Fmo%3E%3C%2Fmover%3E%3C%2Fmrow%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmrow%3E%3C%2Fmrow%3E%3C%2Fmstyle%3E%3Cmrow%3E%3Cmo%3E%28%3C%2Fmo%3E%3Cmrow%3E%3Cmsub%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmi%3Ei%3C%2Fmi%3E%3C%2Fmsub%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmover+accent%3D%22true%22%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmo+stretchy%3D%22true%22%3E%C2%AF%3C%2Fmo%3E%3C%2Fmover%3E%3C%2Fmrow%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmrow%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E800%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
.
附:相关系数
,
;相关系数
,则相关性很强,
的值越大,相关性越强.