薛真 · 2020年02月25日
问题如下：
If X1 and X2 both have univariate normal distributions, is the joint distribution of X1 and X2 a bivariate normal?
选项：
解释：
Not necessarily.
It is possible that the joint is not a bivariate normal if the dependence structure between X1 and X2 is different from what is possible with a normal. The distribution that generated the data points plotted below has normal marginals, but this pattern of dependence is not possible in a normal that always appear elliptical.
翻一下答案
NO.PZ2020010304000008问题如下 If X1 anX2 both have univariate normstributions, is the joint stribution of X1 anX2 a bivariate normal?Not necessarily. It is possible ththe joint is not a bivariate normif the pennstructure between X1 anX2 is fferent from whis possible with a normal. The stribution thgeneratethe ta points plottebelow hnormmarginals, but this pattern of pennis not possible in a normthalways appeelliptical.“两个变量各自服从正态分布，这两个变量的联合分布不一定服从正态分布，得有前提条件就是它们是互相独立的或者相关性为0（事实上相关性为0就可以了，互相独立的条件更强）。”老师好，这里的“事实上相关性为0就可以了”是指p，也就是无线性关系就行？
NO.PZ2020010304000008 问题如下 If X1 anX2 both have univariate normstributions, is the joint stribution of X1 anX2 a bivariate normal? Not necessarily. It is possible ththe joint is not a bivariate normif the pennstructure between X1 anX2 is fferent from whis possible with a normal. The stribution thgeneratethe ta points plottebelow hnormmarginals, but this pattern of pennis not possible in a normthalways appeelliptical. 这道题是什么意思？考点是什么？
NO.PZ2020010304000008 问题如下 If X1 anX2 both have univariate normstributions, is the joint stribution of X1 anX2 a bivariate normal? Not necessarily. It is possible ththe joint is not a bivariate normif the pennstructure between X1 anX2 is fferent from whis possible with a normal. The stribution thgeneratethe ta points plottebelow hnormmarginals, but this pattern of pennis not possible in a normthalways appeelliptical.
可以一下答案么
