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设随机变量X~t(n), Y~F(1, n).给定a(0c} =a,求P|Y>c<sup>2</sup>|的值.
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若随机变量X~N(2,σ^2),且P(2
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设随机变量X~N(μ,4<sup>2</sup>),Y~N(μ,5<sup>2</sup>),记p<sup>1</sup>=P{X≤μ-4},p<sub>2</sub>=P{Y≥μ+5},则( ).
A.p<sub>1</sub>=p<sub>2</sub>;
B.p<sub>1</sub><p<sub>2</sub>:
C.p<sub>1</sub>>p<sub>2</sub>;
D.p<sub>1</sub>,p<sub>2</sub>无法比较
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已知X<sub>1</sub>,X<sub>2</sub>,…,X<sub>6</sub>是来自正态总体N(0,σ<sup>2</sup>)的简单随机样本.且 求a和n. 解题
已知X<sub>1</sub>,X<sub>2</sub>,…,X<sub>6</sub>是来自正态总体N(0,σ<sup>2</sup>)的简单随机样本.且
<img src='https://img2.soutiyun.com/ask/2020-08-10/96589894787285.png' />
求a和n.
解题提示 根据t分布的定义来求.
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设随机变量.则()。A.U~X<sup>2</sup>(n}B.U~x<sup>2</sup>(n-I)C.U~F(n.1)D.U~F(1.n)
设随机变量<img src='https://img2.soutiyun.com/ask/2020-07-27/964689141865362.png' />.则()。
A.U~X<sup>2</sup>(n}
B.U~x<sup>2</sup>(n-I)
C.U~F(n.1)
D.U~F(1.n)
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设 为来自总体N(μ,σ2)的简单随机样本, 为样本均值,已知 是σ<sup>2</sup>的无偏估计(或ET=σ<sup>2</sup>),
设<img src='https://img2.soutiyun.com/ask/2020-11-18/974563559946235.png' />为来自总体N(μ,σ2)的简单随机样本,<img src='https://img2.soutiyun.com/ask/2020-11-18/974563569546784.png' />为样本均值,已知<img src='https://img2.soutiyun.com/ask/2020-11-18/974563615737426.png' />是σ<sup>2</sup>的无偏估计(或ET=σ<sup>2</sup>),则常数C必为()
A.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563625160965.png' />
B.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563634424495.png' />
C.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563643532016.png' />
D.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563651352464.png' />
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设随机变量X与Y相互独立且分别服从正态分布N(μ,σ<sup>2</sup>)与N(μ,2σ<sup>2</sup>),其中σ是未知参数且σ
设随机变量X与Y相互独立且分别服从正态分布N(μ,σ<sup>2</sup>)与N(μ,2σ<sup>2</sup>),其中σ是未知参数且σ>0.记Z=X-Y.
(I)求Z的概率f(z;σ<sup>2</sup>)
(II)设<img src='https://img2.soutiyun.com/ask/2020-11-18/974564587212992.png' />为来自总体Z的简单随机样本,求σ<sup>2</sup>的最大似然估计量<img src='https://img2.soutiyun.com/ask/2020-11-18/974564610926348.png' />
(III)证明<img src='https://img2.soutiyun.com/ask/2020-11-18/974564610926348.png' />为σ<sup>2</sup>的无偏估计量.
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设总体X服从正态分布N(μ,σ<sup>2</sup>)(σ>0).从该总体中抽取简单随机样本 ,其样本均值为 求统计量
设总体X服从正态分布N(μ,σ<sup>2</sup>)(σ>0).从该总体中抽取简单随机样本<img src='https://img2.soutiyun.com/ask/2020-11-18/974556174244797.png' />,其样本均值为<img src='https://img2.soutiyun.com/ask/2020-11-18/974556183114305.png' />求统计量<img src='https://img2.soutiyun.com/ask/2020-11-18/974556216981242.png' />的数学期望EY.
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设随机变量X与Y独立同分布,且E(X)=μ,Var(X)=σ<sup>2</sup>,试求E(X-Y)<sup>2</sup>.
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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。
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设总体X服从正态分布N(μ, σ<sup>2</sup>) (σ>0),从总体中抽取简单随机样本,其样本均值为求统计量的
设总体X服从正态分布N(μ, σ<sup>2</sup>) (σ>0),从总体中抽取简单随机样本<img src='https://img2.soutiyun.com/ask/2020-08-09/965846856163765.png' />,其样本均值为<img src='https://img2.soutiyun.com/ask/2020-08-09/965846906898667.png' />求统计量<img src='https://img2.soutiyun.com/ask/2020-08-09/965846894326948.png' /><img src='https://img2.soutiyun.com/ask/2020-08-09/965846932984159.png' />的数学期望。
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设 是来自总体X~N(μ,σ<sup>2</sup>)的简单随机样本,记求(I)E(Y);(II)D(Y).
设<img src='https://img2.soutiyun.com/ask/2020-11-18/974556250959185.png' />是来自总体X~N(μ,σ<sup>2</sup>)的简单随机样本,记<img src='https://img2.soutiyun.com/ask/2020-11-18/974556263092879.png' />
求(I)E(Y);
(II)D(Y).
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设随机变量X-N(μ,σ<sup>2</sup>),利用标准正态分布函数表,求:(1)P(μ-0.32σ< χ< μ+0.32σ);(2)p(μ+0.69σ< χ< μ+1.15σ);(3)p(χ- μ|>2.58σ).
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随机变量X~N(μ<sub>1</sub>,σ<sub>1</sub><sup>2</sup>),Y~N(μ<sub>2</sub>,σ<sub>2</sub><sup>2</sup>),且P{|X-μ<sub>1</sub>|<1}>P{|Y-μ<sub>2</sub>|<1},则正确的是[].(A)σ<sub>1</sub><σ<sub>2</sub>;(B)σ<sub
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设X<sub>1</sub>,X<sub>2</sub>,...Xn是相互独立的随机变量,且有E(X<sub>1</sub>)=u,D(X<sub>1</sub>)=o<sup>2</sup>,1,2....n,
设X<sub>1</sub>,X<sub>2</sub>,...Xn是相互独立的随机变量,且有E(X<sub>1</sub>)=u,D(X<sub>1</sub>)=o<sup>2</sup>,1,2....n,记
<img src='https://img2.soutiyun.com/ask/2021-01-13/97941085791645.png' />
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已知某种材料的抗压强度X~N(μ,σ<sup>2</sup>),现随机地抽取10个试件进行抗压试验,测得数据如下:482 493 457 471 510 446 435 418 394 469(1)求平均抗压强度μ的置信水平为95%的置信区间;(2)若已知σ=30,求平均抗压强度μ的置信水平为95%的置信区间;(3)求σ的置信水平为95%的置信区间.
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设随机变量X和Y相互独立且都服从正态分布N(0,3<sup>2</sup>),而X<sub>1</sub>,X<sub>2</sub>
设随机变量X和Y相互独立且都服从正态分布N(0,3<sup>2</sup>),而X<sub>1</sub>,X<sub>2</sub>,...,X<sub><span style="font-size: 13.3333px;">n</span></sub>和Y<sub>1</sub>,Y<sub>2</sub>,...,Y<sub>n</sub>分别是来自总体x和Y的样本.则统计量<img src='https://img2.soutiyun.com/ask/2020-09-30/970333024845808.png' />服从()分布,参数为()。
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设X为随机变量且EX=μ,DX=σ<sup>2</sup>,a>0为常数,则由切比雪夫不等式,有().
设X为随机变量且EX=μ,DX=σ<sup>2</sup>,a>0为常数,则由切比雪夫不等式,有<img src='https://img2.soutiyun.com/ask/2020-10-05/970774230821168.jpg' />().
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设总体X~N(μ,σ<sup>2</sup>),μ,σ<sup>2</sup>,未知,X1,...,Xn是X的简单随机样本,则μ的置信水平至少为0.90
设总体X~N(μ,σ<sup>2</sup>),μ,σ<sup>2</sup>,未知,X1,...,Xn是X的简单随机样本,则μ的置信水平至少为0.90的置信区间为()。
<img src='https://img2.soutiyun.com/ask/2021-01-07/978868222705221.jpg' />
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设X<sub>1</sub>,…,X<sub>n</sub>为抽自正态总体N(μ,σ<sup>2</sup>)的简单随机样本,试证为枢轴量,其中k为已知常数
设X<sub>1</sub>,…,X<sub>n</sub>为抽自正态总体N(μ,σ<sup>2</sup>)的简单随机样本,试证
<img src='https://img2.soutiyun.com/ask/2020-08-04/965410591189968.png' />
为枢轴量,其中k为已知常数,
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设随机变量X与Y独立,X~N(μ,a<sub>1</sub><sup>2</sup>),Y~N(μ2,a<sup>2</sup><sub>2</sub>),求:(1)随机变量函数Z<sub>1</sub>=aX+bY的数学期望与方差,其中a及b为常数:(2)随机变量函数Z<sub>2</sub>=XY的数学期望与方差.
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设 ,是来自总体N(0,σ<sup>2</sup>)的简单随机样本,则可以构造未知参数σ<sup>2</sup>的无偏估计量(或数学
设<img src='https://img2.soutiyun.com/ask/2020-11-18/974562941547865.png' />,是来自总体N(0,σ<sup>2</sup>)的简单随机样本,则可以构造未知参数σ<sup>2</sup>的无偏估计量(或数学期望为σ<sup>2</sup>的统计量)()
A.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563028033812.png' />
B.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563036905319.png' />
C.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563044501754.png' />
D.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563052164192.png' />
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设X<sub>1</sub>,X<sub>2</sub>,…,X<sub>n</sub>是来自正态总体N(μ,σ<sup>2</sup>)的简单随机样本,记i=1,2,...,n.求Y<sub>i⌘
设X<sub>1</sub>,X<sub>2</sub>,…,X<sub>n</sub>是来自正态总体N(μ,σ<sup>2</sup>)的简单随机样本,记
<img src='https://img2.soutiyun.com/ask/2020-08-10/965898914993969.png' />i=1,2,...,n.求Y<sub>i</sub>服从的分布及相应的概率密度函数.
解题提示 相互独立的正态分布的随机变量的线性组合仍服从正态分布.
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设 为来自总体N(μ,σ<sup>2</sup>)(σ>0)的简单随机样本;令 则()A.B.C.D.
设<img src='https://img2.soutiyun.com/ask/2020-11-18/974555447058205.png' />为来自总体N(μ,σ<sup>2</sup>)(σ>0)的简单随机样本;令<img src='https://img2.soutiyun.com/ask/2020-11-18/974555483547292.png' />则()
A.<img src='https://img2.soutiyun.com/ask/2020-11-18/974555514524064.png' />
B.<img src='https://img2.soutiyun.com/ask/2020-11-18/974555523007549.png' />
C.<img src='https://img2.soutiyun.com/ask/2020-11-18/974555531280022.png' />
D.<img src='https://img2.soutiyun.com/ask/2020-11-18/974555539864513.png' />