【r2和调整的r2】回归分析中用R2还是调整的R2来说明能解释百分之几因变量_数学_ijLW03MK70
编辑： admin 2017-15-06
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大家好像用惯R平方了.其实你查一下CNKI,有一篇文献说过：“随着自变量个数的增加,余差平方和逐步减少,确定系数R2随之增大.”所以要对R平方进行调整,方法有很多种,不知道SPSS里用的是什么算法.应该调整有R平方更能解释因变量.
和你讨论而已.
其他同学给出的参考思路：
用调整的 不调整受自变量数目影响 调整的不受
互助这道作业题的同学还参与了下面的作业题
题1： 标准化回归系数Beta的大小与每一变量对因变量的贡献量R2的大小,不是一一对应的?这是为什么?两者不统一的时候该看那个值呢?beta与R2有什么关系呢[数学科目]
每一个变量对因变量的贡献量,你是看的哪个指标?
题2： spss线性回归后算出决定系数r2大于1?[英语科目]
The R-Squared tells you how much your ability to predict is improved by using the regression line, compared with not using it.
The assumption is that if you don't use your regression line, you'll ignore what X is and use the mean of your Y values as your prediction.
The least possible improvement is 0. This is if the regression line is no help at all. You might as well use the mean of the Y values for your prediction.
The most possible improvement is 1. This is if the regression line fits the data perfectly.
That is why the R-squared is always between 0 and 1. The regression line is never worse than worthless (0), and it can't be better than perfect (1).
All this is based on the assumptions behind using least squares being true. If those assumptions are not true, then it is possible that using the regression line to predict could be worse than worthless.
The formula for the R-squared, and the assumptions behind using least squares regression, are in the course booklet.
If your regression results show an R-squared of less than 0 or greater than 1, then one of these is true:
1、There is a calculation error, or
2、Your results are reporting an "adjusted" R-squared. (The template you have constructed does not do this, but some commercial statistical software does report an adjusted R-squared.) An "adjusted" R-squared tries to allow for the fact that an X variable that is really completely unrelated to your Y variable will probably have some relationship to Y in your data just by luck. The adjusted R-squared reduces the R-squared by how much fit would probably happen just by luck. Sometimes this reduction is more than the calculated R-squared, so you wind up with a negative adjusted R-squared.
以上内容见参考资料
大致说来是两种情况：
1、计算错误
2、商业软件展现的可能是调整后R方.
你的情况应该就是第二种了,可以好好看看第二种情况的解释.有问题Hi我.
题3： 多元回归分析数据分析结果中的R2,F值,B,t值,beta分别是什么,
拟合度,F统计量,回归系数,t统计量,回归系数
我经常帮别人做这类的数据统计分析的
题4： F=GM1M2/R2的具体解释?[物理科目]
万有引力公式,书上不有嘛?你在考试?
题5： 圆锥侧面积公式2个公式怎么会相等（n/360×π×R2=1/2LR）,请详细解说每一个公式.并说明如何相等[数学科目]
圆锥体的侧面积公式出现两种：
S=1/2RL.（R为圆锥体底面圆的周长,L为圆锥的母线长）
S=πRL.（R为圆锥体底面圆的半径,L为圆锥的母线长）
都是正确的,只是途径不一样.
求圆锥体的侧面积,先要把圆锥体变形.
设想沿着圆锥一条母线剪断,然后展开,可以得到一个扇形,求它的面积就可以了.
求扇形面积有两种方法,结果就有了以上两种不同的表达式.
表达式 1
利用积分原理.
设想扇形是由若干n个等腰三角形拼成,这些三角形是足够小,使得其底边长 = R/n (R是圆锥体地面圆的周长,即扇形的弧长）,高 = 侧边长L（L为扇形的半径,亦为圆锥体的母线）.
则扇形面积
S = n(三角形个数) X s(单位等腰三角形的面积）
= n X (1/2 X R/n X L)
= 1/2RL
表达式 2
利用弧长.
扇形面积 / 圆总面积 = 弧长 / 圆周长
扇形面积
S = 圆总面积(扇形所属圆） X (弧长 / 圆周长)
= 圆总面积 X (圆锥地面周长 / 扇形所属圆形周长）
= πL2(L为母线长) X (2πR / 2πL)
= πLR