统计代写|回归分析作业代写Regression Analysis代考|Parameter Interpretation in Interaction Models

Doug I. Jones

Doug I. Jones

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如果你也在 怎样代写回归分析Regression Analysis 这个学科遇到相关的难题,请随时右上角联系我们的24/7代写客服。回归分析Regression Analysis回归中的概率观点具体体现在给定X数据的特定固定值的Y数据的可变性模型中。这种可变性是用条件分布建模的;因此,副标题是:“条件分布方法”。回归的整个主题都是用条件分布来表达的;这种观点统一了不同的方法,如经典回归、方差分析、泊松回归、逻辑回归、异方差回归、分位数回归、名义Y数据模型、因果模型、神经网络回归和树回归。所有这些都可以方便地用给定特定X值的Y条件分布模型来看待。

回归分析Regression Analysis条件分布是回归数据的正确模型。它们告诉你,对于变量X的给定值,可能存在可观察到的变量Y的分布。如果你碰巧知道这个分布,那么你就知道了你可能知道的关于响应变量Y的所有信息,因为它与预测变量X的给定值有关。与基于R^2统计量的典型回归方法不同,该模型解释了100%的潜在可观察到的Y数据,后者只解释了Y数据的一小部分,而且在假设几乎总是被违反的情况下也是不正确的。

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统计代写|回归分析作业代写Regression Analysis代考|Parameter Interpretation in Interaction Models

统计代写|回归分析作业代写Regression Analysis代考|Parameter Interpretation in Interaction Models

Parameter interpretation in interaction models is complicated by the fact that the $X$ variables in the model are functionally related to each other. Thus, the standard “increase $X_1$ by +1 while holding all other terms fixed” interpretation cannot be used, because you cannot increase $X_1$ by +1 while simultaneously keeping both $X_2$ and $X_1 X_2$ fixed.

However, you can increase $X_1$ while holding $X_2$ fixed. Consider two groups of potentially observable data, one where $X_1=x_1$ and $X_2=x_2$, and the other where $X_1=x_1+1$ and $X_2=x_2$. The interpretation of the parameters then follows logically from the model, as in all other cases you have seen (and will see): If the no interaction model is truly the data-generating process, then the following conclusions are mathematically true.
$$
\begin{aligned}
& \text { Group 1: } X_1=x_1, X_2=x_2: \text { Here, } \mathrm{E}\left(Y \mid X_1=x_1, X_2=x_2\right)=\beta_0+\beta_1 x_1+\beta_2 x_2+\beta_3 x_1 x_2 \
& \text { Group 2: } X_1=x_1+1, X_2=x_2: \text { Here, } \
& \qquad \begin{aligned}
\mathrm{E}\left(Y \mid X_1=x_1, X_2=x_2\right) & =\beta_0+\beta_1\left(x_1+1\right)+\beta_2 x_2+\beta_3\left(x_1+1\right) x_2 \
& =\beta_0+\beta_1 x_1+\beta_2 x_2+\beta_3 x_1 x_2+\left(\beta_1+\beta_3 x_2\right) \
& =(\text { Group } 1 \text { mean })+\left(\beta_1+\beta_3 x_2\right)
\end{aligned}
\end{aligned}
$$
Thus, in the interaction model, the coefficient $\beta_1$ does not measure the effect of increasing $X_1$ when $X_2$ is held constant because there is a different effect for every possible $X_2=x_2$ (namely, $\beta_1+\beta_3 x_2$ ). You can interpret $\beta_1$ as the increase in $\mathrm{E}(Y)$ per unit increase in $X_1$ when $X_2=0$, but now we are back to the interpretation that is practically useless when the $X_2$ data do not cover 0.0. Still, just like the intercept term $\beta_0$ is necessary in regression, regardless of its interpretability or “significance,” the $\beta_1$ term is necessary in the interaction model, regardless of its interpretability or “significance.” See Section 9.4 of this chapters for elaboration on this concept.

统计代写|回归分析作业代写Regression Analysis代考|Effect of Misanthropy on Support for Animal Rights: The Moderating Effect of Idealism

The paper “Misanthropy, idealism, and attitudes toward animals,” (Wuensch et al. 2002) develops theory and analyzes data showing that animal rights support is related to misanthropy for non-idealistic students, but that animal rights support is not strongly related to misanthropy for idealist students. They developed and validated a survey instrument to measure three variables, $Y=$ Support for Animal Rights, $X_1=$ Misanthropy, and $X_2=$ Idealism, as averages of responses (typically in the 1,2,3,4,5 scale) to three sets of questions on the survey. As averages, these data are more continuous than the 1,2,3,4,5 scale itself, and hence better modeled using normal distributions than are the actual 1,2,3,4,5 data.

The model that allows the effect of $X_1$ on $Y$ to depend on the value of $X_2$ (i.e., the moderation model) is the interaction model
$$
Y_i \mid X_{i 1}=x_{i 1}, X_{i 2}=x_{i 2} \sim_{\text {ind }} \mathrm{N}\left(\beta_0+\beta_1 x_{i 1}+\beta_2 x_{i 2}+\beta_3 x_{i 1} x_{i 2}, \sigma^2\right)
$$

统计代写|回归分析作业代写Regression Analysis代考|Parameter Interpretation in Interaction Models

回归分析代写

统计代写|回归分析作业代写Regression Analysis代考|Parameter Interpretation in Interaction Models

交互模型中的参数解释由于模型中的$X$变量在功能上相互关联而变得复杂。因此,不能使用标准的“将$X_1$增加+1,同时保持所有其他项固定”解释,因为您不能将$X_1$增加+1,同时保持$X_2$和$X_1 X_2$固定。

但是,您可以在保持$X_2$固定的同时增加$X_1$。考虑两组潜在的可观察数据,一组是$X_1=x_1$和$X_2=x_2$,另一组是$X_1=x_1+1$和$X_2=x_2$。然后,参数的解释从逻辑上遵循模型,就像在您已经看到(并将看到)的所有其他情况中一样:如果无交互模型确实是数据生成过程,那么以下结论在数学上是正确的。
$$
\begin{aligned}
& \text { Group 1: } X_1=x_1, X_2=x_2: \text { Here, } \mathrm{E}\left(Y \mid X_1=x_1, X_2=x_2\right)=\beta_0+\beta_1 x_1+\beta_2 x_2+\beta_3 x_1 x_2 \
& \text { Group 2: } X_1=x_1+1, X_2=x_2: \text { Here, } \
& \qquad \begin{aligned}
\mathrm{E}\left(Y \mid X_1=x_1, X_2=x_2\right) & =\beta_0+\beta_1\left(x_1+1\right)+\beta_2 x_2+\beta_3\left(x_1+1\right) x_2 \
& =\beta_0+\beta_1 x_1+\beta_2 x_2+\beta_3 x_1 x_2+\left(\beta_1+\beta_3 x_2\right) \
& =(\text { Group } 1 \text { mean })+\left(\beta_1+\beta_3 x_2\right)
\end{aligned}
\end{aligned}
$$
因此,在相互作用模型中,当$X_2$保持不变时,系数$\beta_1$不能衡量增加$X_1$的效果,因为每种可能的$X_2=x_2$(即$\beta_1+\beta_3 x_2$)都有不同的效果。您可以将$\beta_1$解释为$X_2=0$时每单位$X_1$的增加量$\mathrm{E}(Y)$的增加量,但现在我们又回到了当$X_2$数据不包括0.0时实际上无用的解释。然而,就像截距项$\beta_0$在回归中是必要的一样,不管它的可解释性或“重要性”如何,$\beta_1$项在交互模型中也是必要的,不管它的可解释性或“重要性”如何。参见本章第9.4节对这个概念的详细阐述。

统计代写|回归分析作业代写Regression Analysis代考|Effect of Misanthropy on Support for Animal Rights: The Moderating Effect of Idealism

论文“厌世、理想主义和对动物的态度”(Wuensch et al. 2002)发展了理论并分析了数据,表明动物权利支持与非理想主义学生的厌世有关,但动物权利支持与理想主义学生的厌世关系并不强。他们开发并验证了一个调查工具来测量三个变量,$Y=$对动物权利的支持,$X_1=$厌世和$X_2=$理想主义,作为对调查中三组问题的平均回答(通常为1,2,3,4,5级)。作为平均值,这些数据比1,2,3,4,5尺度本身更连续,因此使用正态分布比实际的1,2,3,4,5数据更好地建模。

允许$X_1$对$Y$的影响依赖于$X_2$的值的模型(即调节模型)是交互模型
$$
Y_i \mid X_{i 1}=x_{i 1}, X_{i 2}=x_{i 2} \sim_{\text {ind }} \mathrm{N}\left(\beta_0+\beta_1 x_{i 1}+\beta_2 x_{i 2}+\beta_3 x_{i 1} x_{i 2}, \sigma^2\right)
$$


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