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单选题设与为两个随机变量,则下列式子正确的是( )

A.

B.

C.

D.

概率论与数理统计课程封面

学科：概率论与数理统计

时间：2023-12-13 14:12:18

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下列表述中错误的是

A. 期望是什平均值B. 方差是数据的差距值C. 期望越大,方差越大D. 方差也是一种期望

若随机变量<img src="https://p.ananas.chaoxing.com/star3/origin/968f3e020e54660cfda17add8873662e.png">在区间<img src="https://p.ananas.chaoxing.com/star3/origin/c9ab42a06b165e30cab5f328ec8d763c.png">上服从均匀分布,<img src="https://p.ananas.chaoxing.com/star3/origin/c000c6ba9988b56cbe2bdcf4a33d1e48.png">,则区间<img src="https://p.ananas.chaoxing.com/star3/origin/c9ab42a06b165e30cab5f328ec8d763c.png">为

A. <img src="https://p.ananas.chaoxing.com/star3/origin/ce0056e944fa2544d93aeb1ddc42ec6f.png">B. <img src="https://p.ananas.chaoxing.com/star3/origin/6211a6309238d0e5ae7d1dc48d5d6865.png">C. <img src="https://p.ananas.chaoxing.com/star3/origin/c9f2631b9f116e6fc5c80f99fc2a290f.png">D. <img src="https://p.ananas.chaoxing.com/star3/origin/132c3467cff3433337e499d1b1ccc655.png">

设随机变量<img src="https://p.ananas.chaoxing.com/star3/origin/968f3e020e54660cfda17add8873662e.png">的分布函数为<img src="https://p.ananas.chaoxing.com/star3/origin/30fa3e328884d4e7603748f7b5c31f7d.png">,则 <img src="https://p.ananas.chaoxing.com/star3/origin/75476492c8312f6cc376e5cece168084.png">

A. <img src="https://p.ananas.chaoxing.com/star3/origin/4c2c5491af6dc4bc517515f812c01923.png">B. <img src="https://p.ananas.chaoxing.com/star3/origin/e1de9cabc4b912495885f625ceedc5f2.png">C. <img src="https://p.ananas.chaoxing.com/star3/origin/401ea451d082d7083427f988afb48e92.png">D. <img src="https://p.ananas.chaoxing.com/star3/origin/81bdfae5d2dcaca6fd4e56e0cf61d909.png">

设<img src="https://p.ananas.chaoxing.com/star3/origin/968f3e020e54660cfda17add8873662e.png">与<img src="https://p.ananas.chaoxing.com/star3/origin/d65d437507eb7187ad8a9ce23f52b05f.png">为两个独立的随机变量,其方差分别为6和3,则<img src="https://p.ananas.chaoxing.com/star3/origin/3ff8f79dd5605ce1cfd153f3c76118db.png">

A. 9B. 15C. 21D. 27

设<img src="https://p.ananas.chaoxing.com/star3/origin/968f3e020e54660cfda17add8873662e.png">与<img src="https://p.ananas.chaoxing.com/star3/origin/d65d437507eb7187ad8a9ce23f52b05f.png">为两个随机变量,则下列式子正确的是( )

A. <img src="https://p.ananas.chaoxing.com/star3/origin/0d1f0a884200c009791bf534942da852.png">B. <img src="https://p.ananas.chaoxing.com/star3/origin/1ce533e8ba5563eb6aeee57e10d114ca.png">C. <img src="https://p.ananas.chaoxing.com/star3/origin/63873bce14869b2b07e6d6ab551f81bb.png">D. <img src="https://p.ananas.chaoxing.com/star3/origin/9260e1213793c75ad0c3376cb26bb510.png">

设X为随机变量,且E(X)=1,D(X)=2,则E(2X+3)= ,D(2X+3)=

设随机变量X的方差为2,则D(2X+1)=____

方差就是标准差

方差是随机变量<img src="/ananas/latex/p/579">的函数<img src="/ananas/latex/p/2112160">的期望

设随机变量<img src="https://p.ananas.chaoxing.com/star3/origin/968f3e020e54660cfda17add8873662e.png">的概率分布为<img src="https://p.ananas.chaoxing.com/star3/origin/b8017d4d2ad2ad9e61e36d7e85fce6de.png">则<img src="https://p.ananas.chaoxing.com/star3/origin/ff853f6f57e3a4a55d50663e4f103b88.png">=29/36

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