设（）是来自总体X的样本，则下列哪项不是总体均值的无偏估计量（ )http://mooc.chaoxing.com/ananas/latex/p/106794

A . （30.88，32.63） B . （31.45，31.84） C . （31.62，31.97） D . （30.45，31.74）

A .https://assets.asklib.com/psource/2015102915530155953.jpg B .https://assets.asklib.com/psource/2015102915531942539.jpg C .https://assets.asklib.com/psource/2015102915532911179.jpg D .https://assets.asklib.com/psource/2015102915534171578.jpg

A . ['['X1-X2+X3B . 2X3-μC .https://assets.asklib.com/psource/2015101517580884933.jpg D .https://assets.asklib.com/psource/2015101517581233582.jpg E .https://assets.asklib.com/psource/2015101517581652360.jpg

A . ['x5B .https://assets.asklib.com/psource/2015103009361331257.jpg C . nD .https://assets.asklib.com/psource/2015103009362870429.jpg

设总体X～N(μ，σ²)，其中σ²未知，若样本容量n和置信度1-a均不变，则对于不同的样本观测值，总体均值μ的置信区间的长度( )

设X1，X2，…，X16是来自总体X~N(4，б2)的简单随机样本，б2已知，令<img src='https://img2.soutiyun.com/ask/2019-07-19/932375682552355.png' />，则统计量<img src='https://img2.soutiyun.com/ask/2019-07-19/932375692068372.png' />服从的概率密度函数为()

设总体的概率密度<img src='https://img2.soutiyun.com/ask/2020-11-18/974557682083041.png' />是来自总体x的简单随机样本，<img src='https://img2.soutiyun.com/ask/2020-11-18/974557703336256.png' /> 求(I)ET; (II)DT.

A.(30.88，32.63) B.(31.45，31.84) C.(31.62，31.97) D.(30.45，31.74)

设X₁，X₂，...X_n(n≥2)为来自正态总体N(0，1)的简单随机样本，<img src='https://img2.soutiyun.com/ask/2020-07-31/965062468168756.png' />为样本均值，S²为样本方差，则正确的是()。 <img src='https://img2.soutiyun.com/ask/2020-07-31/965062477119268.png' />

如图所示，设总体<img src='https://img2.soutiyun.com/ask/2020-07-27/96469314696044.png' />为来自总体X的一个简单随机样本.<img src='https://img2.soutiyun.com/ask/2020-07-27/9646931619863.png' />分别为其样本均值和样本方差. (1)证明对任意<img src='https://img2.soutiyun.com/ask/2020-07-27/964693245155057.jpg' />的常数的期望为σ²; (2)求常数c,使得<img src='https://img2.soutiyun.com/ask/2020-07-27/964693265241206.png' />达到最小值.

设总体X～N(μ，0.09)，随机抽取容量为36的一个样本，其样本均值为，则总体均值μ的90%的置信区间是（）。 <img src='https://img2.soutiyun.com/ask/uploadfile/2556001-2559000/28324e2cb3936e7a8d64a40813e01950.gif' />

设(X₁,X₂,...,X₁₅)是来自正态总体N(0,9)的简单随机样本,则统计量Y<img src='https://img2.soutiyun.com/ask/2020-10-05/9707790061243.jpg' />的概率分布是参数为()的()分布.

设<img src='https://img2.soutiyun.com/ask/2020-11-18/974563559946235.png' />是来自总体X~N(μ,σ²)的样本,其中μ已知,σ²＞0为未知参数,样本均值为<img src='https://img2.soutiyun.com/ask/2020-11-18/974563569546784.png' />,则σ²的最大似然估计量为（） A.<img src='https://img2.soutiyun.com/ask/2020-11-18/97456369359988.png' /> B.<img src='https://img2.soutiyun.com/ask/2020-11-18/97456370198636.png' /> C.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563711307893.png' /> D.<img src='https://img2.soutiyun.com/ask/2020-11-18/974563720210402.png' />

A．2 B．3 C．4 D．5

设总体X服从参数为P的0-1分布,则来自总体X的简单随机样本<img src='https://img2.soutiyun.com/ask/2020-11-18/974554990191073.png' />的概率分布为___

设<img src='https://img2.soutiyun.com/ask/2020-11-18/974563944699242.png' />是来自区间[-a,a].上均匀分布的总体X的简单随机样本，则参数a的矩估计量<img src='https://img2.soutiyun.com/ask/2020-11-18/974563958950057.png' />=____.

x₁,x₂,…,x₃是来自总体N(μ,0.3²)的样本值,且样本的均值<img src='https://img2.soutiyun.com/ask/2020-09-30/97034316026152.png' />=21.8.则μ的置信度为0.95的置信区间为().

设总体<img src='https://img2.soutiyun.com/ask/2021-01-02/978470547656441.png' />是取自该总体的样本，求样本均值Y=(X₁，X₂)的密度函数。

设总体X服从标准正态分布，X₁，X₂，...，X_n是来自X的样本，则统计量<img src='https://img2.soutiyun.com/ask/2021-01-04/978607698915946.jpg' />服从()分布，参数为()。

设总体X~N(01),X1、X2、X3、X4..X5为来自总体X的简单随机样本，<img src='https://img2.soutiyun.com/ask/2020-07-27/964689261739219.png' />分别为样本均值和样本标准差,则下列结论中正确的为()。 A.<img src='https://img2.soutiyun.com/ask/2020-07-27/964689251838652.png' /> B.<img src='https://img2.soutiyun.com/ask/2020-07-27/964689275003977.png' /> C.<img src='https://img2.soutiyun.com/ask/2020-07-27/964689286002606.png' /> D.<img src='https://img2.soutiyun.com/ask/2020-07-27/964689292953004.png' />

设总体X~E(λ),则来自总体X的样本<img src='https://img2.soutiyun.com/ask/2020-11-18/974554950987831.png' />的联合概率密度<img src='https://img2.soutiyun.com/ask/2020-11-18/97455496146043.png' />=___