甲乙两种牌子的手表,它们的日走时差分别为X与Y(单位:秒),已知X与Y分别有如表1.2-1所示的分布列(概率函数),则下列结论正确的有()。<img src='https://img2.soutiyun.com/ask/uploadfile/3066001-3069000/38b495834a21e1b6796b5b8ff843b1ac.jpg' />
随机变量X的概率密度<img src='https://img2.soutiyun.com/latex/latex.action' />,则D(X)=( )
f(x)在x=x<sub>0</sub>处有定义是<img src='https://img2.soutiyun.com/ask/2020-02-17/950797744758253.png' />存在的( )。
设<img src='https://img2.soutiyun.com/latex/latex.action' />,则点x=1是f(x)的( )。
设二维随机变量(X,Y)的分布函数为<img src='https://img2.soutiyun.com/ask/uploadfile/6663001-6666000/45f51949890b44017e315c766cce4df5.png' />,则常数A,B分别为( ).
设函数g(x)=1+x,且当x≠0时,<img src='https://img2.soutiyun.com/ask/2020-02-18/950885721858992.png' />,则<img src='https://img2.soutiyun.com/ask/2020-02-18/950885746436467.png' />等于( )
设随机变量X的概率密度为<img src='https://img2.soutiyun.com/latex/latex.action' />,则E(X)=( )
设随机变量X的分布函数<img src='https://img2.soutiyun.com/latex/latex.action' />,则E(X)=( )
若<img src='https://img2.soutiyun.com/ask/2020-03-10/952728203989995.png' />,x≠0,且f(x)在x=0处连续,则( ).
X的分布列如表5.1-5所示。其中1≤X≤5,有关P(1<X<5)的下列说法中,正确的有()。<img src='https://img2.soutiyun.com/ask/uploadfile/3927001-3930000/13c8947d4fb2027ae6cf09adb7e92798.jpg' />
如果X~φ(x),而<img src='https://img2.soutiyun.com/latex/latex.action' />,则P(X≤1.5)=( ).
如果f(x)=e<sup>x</sup>,则<img src='https://img2.soutiyun.com/shangxueba/ask/18747001-18750000/18749502/2016071617275141166.jpg' />等于:()<img src='https://img2.soutiyun.com/shangxueba/ask/18747001-18750000/18749502/2016071617274553502.jpg' />
设随机变量X服从指数分布,其概率密度为<img src='https://img2.soutiyun.com/shangxueba/ask/51282001-51285000/51284053/97507319824928.jpg' />,其中θ>0是常数,求E(X),D(X)。
某产品各功能的功能系数和成本系数如下表所示,应列为价值工程优先改进对象的是()功能。<img src='https://img2.soutiyun.com/ask/uploadfile/3930001-3933000/90ab8068c1350c4dd0fec047705d7232.jpg' />
甲公司有一笔闲置资金,拟投资于某证券组合,由X、Y、Z三种股票构成,资金权重分别为40%,30%和30%,β系数分别为2.5,1.5和1。其中X股票投资收益率的概率分布如下:<img src='https://img2.soutiyun.com/exam/2019-09-29/938601918884098.png' />
设X<sub>1</sub>,X<sub>2</sub>,X<sub>3</sub>,X<sub>4</sub>是来自正态总体N(0,3<sup>2</sup>)的简单随机样本,若随机变量<img src='https://img2.soutiyun.com/shangxueba/ask/51402001-51405000/51404692/978102656256342.jpg' />,试求a,b的值,使统计量X服从χ<sup>2</sup>分布,并求其自由度。
<table><tbody><tr><td>正态分布函数<i>f</i>(<i>x</i>)=<img src='https://img2.soutiyun.com/ask/uploadfile/6840001-6843000/f11daf3108007f352c38e099bf8d0ddd.gif' />的图象为<img src='https://img2.soutiyun.com/ask/uploadfile/6840001-6843000/8e31eb990135e28d7de0adb3b27775b1.gif' /></td></tr></tbody></table>
将函数f(x)=x<sup>2</sup>在<img src='https://img2.soutiyun.com/shangxueba/ask/18735001-18738000/18737342/2016071617062459326.jpg' />上展开成余弦级数,其形式为<img src='https://img2.soutiyun.com/shangxueba/ask/18735001-18738000/18737342/2016071617063532608.jpg' /><img src='https://img2.soutiyun.com/shangxueba/ask/18735001-18738000/18737342/2016071617065141640.jpg' />()<img src='https://img2.soutiyun.com/shangxueba/ask/18735001-18738000/18737342/2016071617071375522.jpg' />
下图为一个AOV网,其可能的拓扑有序序列为:<img src='http://static.jiandati.com/c98081e-chaoxing2016-1094214.bin' />
已知随机变量X的分布列为P()
不计杆的分布质量,图示体系的动力自由度为()。<img src='https://img2.soutiyun.com/1/2021-04-07/986665887381569.jpg' />
设随机变量(X,Y)的分布律为 <img src="https://img2.soutiyun.com/shangxueba/ask/19434001-19437000/19435034/c33cb56-chaoxing2016-268566.png"/>则P{X=2|Y=2}=()
计算一维无限深势阱中基态粒子处在x=0到x=L/3区间的几率。设粒子的势能分布函数为:<img src='https://img2.soutiyun.com/ask/2021-02-09/981726779508461.png' />
图示景观分布的省级行政区及简称对应正确的是()。<img src='https://img2.soutiyun.com/1/2021-04-08/986729307920011.png' />