20春学期《概率论》在线平时作业1

adminhan

公交部门承诺某线路每班车到站间隔不超过20分钟，因此每个候车的乘客等待时间超出15分钟的概率最多只有：
A:0.125；
B:0.25；
C:0.5；
D:0.75

在两点分布中，若随机变量X=0时的概率为p,则X=1时的概率为：
A:1－p
B:p
C:1
D:1+p

<div>已知随机变量<span>X的密度函数f(x)=Ae X&gt;=</span>&lambda; f(x)=0 x&lt;&lambda;, (&lambda;&gt;0,A为常数<span>)，则概率P{</span>&lambda;&lt;X&lt;&lambda;+a}（<span>a&gt;0）的值<u><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></u></span></div>
A:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">与<span lang="EN-US">a</span>无关，随</span><span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'Tahoma','sans-serif'; BACKGROUND: white; COLOR: black; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes; mso-fareast-font-family: 宋体">&lambda;</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">的增大而增大</span>
B:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">与<span lang="EN-US">a</span>无关，随</span><span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'Tahoma','sans-serif'; BACKGROUND: white; COLOR: black; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes; mso-fareast-font-family: 宋体">&lambda;</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">的增大而减小</span>
C:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">与</span><span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'Tahoma','sans-serif'; BACKGROUND: white; COLOR: black; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes; mso-fareast-font-family: 宋体">&lambda;</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">无关，随<span lang="EN-US">a</span>的增大而减小</span>
D:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">与</span><span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'Tahoma','sans-serif'; BACKGROUND: white; COLOR: black; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes; mso-fareast-font-family: 宋体">&lambda;</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">无关，随<span lang="EN-US">a</span>的增大而增大 </span>

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-font-kerning: 1.0pt; mso-no-proof: yes; mso-bidi-font-family: 'Times New Roman'">一射手对同一目标独立地进行四次射击，若至少命中一次的概率为80/81，则该射手的命中率为</span>
A:1/3
B:2/3
C:1/6
D:1/4

<p style="TEXT-INDENT: 10.5pt; MARGIN: 0cm 0cm 0pt; mso-char-indent-count: 1.0" class="MsoNormal"><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">设随机变量</span><span lang="EN-US"><font face="Times New Roman">X</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">服从正态分布</span><span lang="EN-US"><font face="Times New Roman">X~N</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">（</span><span lang="EN-US"><font face="Times New Roman">0</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</span><span lang="EN-US"><font face="Times New Roman">1），</font></span><span lang="EN-US"><font face="Times New Roman">Y=2X-1</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，则</span><span lang="EN-US"><font face="Times New Roman">Y~<span style="mso-spacerun: yes">&nbsp;</span></font></span></font></p>
A:<span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">N</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">0</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">，</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">1</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">）</span>
B:<span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">N</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">-1</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">，</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">4</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">）</span>
C:<span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">N</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">-1</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">，</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">1</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">）</span>
D:<span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">N</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">-1</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">，</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt" lang="EN-US">3</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt">）</span>

<div>设随机变量<span>X和Y的方差存在且不等于0，则D（X+Y）=D（X）+D（Y）</span></div><div>是<span>X和Y的<u><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></u></span></div>
A:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">不相关的充分条件，但不是必要条件</span>
B:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">独立的必要条件，但不是充分条件；</span>
C:不相关的充分必要条件；<span><span>&nbsp;&nbsp;&nbsp; </span></span>
D:<div>独立的充分必要条件</div>

3人独立射击同一目标，他们击中目标的概率分别是1|5,1|3,1|4，则目标被击中的概率是
A:3|5
B:2|5
C:7|10
D:4|5

<div align="left">对于任意两个随机变量<span>X和Y，若E（XY）=E(X)E（Y）则<u><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></u></span></div>
A:<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">D</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">（<span lang="EN-US">XY</span>）<span lang="EN-US">=D</span>（<span lang="EN-US">X</span>）<span lang="EN-US">D</span>（<span lang="EN-US">Y</span>）</span>
B:<div>D（<span>X+Y）=D（X）+D（Y）</span></div>
C:<span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes"><span lang="EN-US">X</span>和<span lang="EN-US">Y</span>独立 </span>
D:<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">X</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes">和<span lang="EN-US">Y</span>不独立</span>

<p>设X,Y是两个独立的随机变量，且P(X=1)=0.3，P(Y=2)=0.4,则P（X=1，Y=2）=(&nbsp; ) </p>
A:0.3
B:0.4
C:0.7
D:0.12

<p>有甲乙2批种子，发芽率分别为0.8和0.7，在2批中随机地各取一粒，则两粒种子都发芽的概率为：</p>
A:0.56
B:0.94
C:0.44
D:0.36

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">某人射击中靶概率为</span><span style="FONT-FAMILY: 'Times New Roman','serif'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体" lang="EN-US">3/4,</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">如果直到命中为止，则射击次数为</span><span style="FONT-FAMILY: 'Times New Roman','serif'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体" lang="EN-US">3</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">的概率为</span>
A:27/64
B:9/64
C:3/64
D:1/64

设两个随机变量X和Y的期望分别是6和3，则随机变量2X－3Y的期望是
A:6
B:3
C:12
D:21

袋中有5个白球和3个黑球，从中任取2个球，则取得的2个球同色的概率是
A:0.4624
B:0.8843
C:0.4688
D:0.4623

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-no-proof: yes"><span style="mso-spacerun: yes">&nbsp;</span>将<em style="mso-bidi-font-style: normal"><span lang="EN-US">C,C,E,E,I,N,S</span></em>等<span lang="EN-US">7</span>个字母随机的排成一行，那末恰好排成英文单词<em style="mso-bidi-font-style: normal"><span lang="EN-US">SCIENCE</span></em>的概率</span>
A:1/7!
B:1/1260
C:5!/7!
D:1/640

<p>设两个随机变量X和Y相互独立的同分布：P(X=-1)=P(Y=-1)=1/2，P(X=1)=P(Y=1)=1/2，则下列各式中成立的是（）</p>
A:P(X=Y)=1/2
B:P(X=Y)=1
C:P(X+Y=0)=1/4
D:P(XY=1)=1/4

盆中有5个乒乓球，其中3个新，2个旧的，每次取一球，连续有放回地取两次，以A记&ldquo;第一次取到新球&rdquo;这一事件；以B记&ldquo;第二次取到新球&rdquo;这一事件。则在已知第一次或是第二次取到新球的条件下，第一次取到新球的概率为：
A:P(B|A)
B:P(A|A&cup;B)
C:P(B|A&cup;B)
D:P(A|B)

<p>已知（X,Y）服从二维正态分布，EX₁=u₁，EX₂=u₂，DX=DY=<span style="WHITE-SPACE: normal; TEXT-TRANSFORM: none; WORD-SPACING: 0px; FLOAT: none; COLOR: rgb(0,0,0); FONT: 14px/24px tahoma, arial, 宋体; ORPHANS: 2; WIDOWS: 2; DISPLAY: inline !important; LETTER-SPACING: normal; BACKGROUND-COLOR: rgb(255,255,255); TEXT-INDENT: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">&sigma;²，<span style="WHITE-SPACE: normal; TEXT-TRANSFORM: none; WORD-SPACING: 0px; FLOAT: none; COLOR: rgb(0,0,0); FONT: 14px/24px arial, 宋体, sans-serif; ORPHANS: 2; WIDOWS: 2; DISPLAY: inline !important; LETTER-SPACING: normal; BACKGROUND-COLOR: rgb(255,255,255); TEXT-INDENT: 30px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">&rho;=0，则下列四对随机变量中相互独立的是（)</span></span></p>
A:<p>X与X+Y</p>
B:X与X-Y
C:X+Y与X-Y
D:2X+Y与X-Y

<p>设随机变量X服从正态分布N(0，1），对给定的a属于（0，1），数u_a 满足P{X&gt;u_a}=a,若P{|X|&lt;x}=a,则x等于（）</p>
A:u_a/2
B:u_1-a/2
C:u_(1-a)/2
D:u_1-a

从1,2,3,4,5五个数中，任取两个不同数排成两位数，则所得数位偶数的概率是
A:0.4
B:0.3
C:0.6
D:0.5

从0,1,2，...，9这10个数中随机抽取一个数字，则取到的是奇数的概率是
A:1|2
B:1|3
C:1|4
D:1|5