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1、参数估计(复习)通过对样本的处理,对总体的未知参数(如:数学期望、方差等)作出较好的估计.一.点估计量的求法:1.矩法:①参数:设或称为参数②点估计:设参数未知则构造统计量去估计称为的估计量,为的估计值,估计量、估计值统称估计。这种对未知参数的定值估计称为点估计。③矩法:用样本矩一般步骤是:设,其中参数待估.(i),计算;(ii)由=或即:即:有个估计量例:(P110)设=,求otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiangxi,andDirectorofthenewOff
2、iceinJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,DirectorofNingxiaCountyparty
3、CommitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand19。解:由于=;又=则由#2.极大似然法设,其中未知,则:,得的联合分布称为似然函数解题方法:将似然函数取对数,有:对上式求偏导,并令由k元方程组(似然方程组)求得例:(P118)设,概率密度为=,,试求的极大似然估计.otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiangxi,andDirectorofthenewOffice
4、inJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,DirectorofNingxiaCountypartyCom
5、mitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand19解:的似然函数为两边取对数,得:似然方程为即:的极大似然估计量为#例:(P120)设在上服从均匀分布,,求的极大似然估计量.解:的分布密度为:∴ 似然函数为:显然对无法利用令偏导数等于零的方法求驻点,使得在某点处有:事实上:由,即:所以在上,为的最大值.故得的极大似然估计量为:#otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiang
6、xi,andDirectorofthenewOfficeinJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,Dir
7、ectorofNingxiaCountypartyCommitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand193.顺序统计量法:①总体均值的估计:设 记中位数可用:作为总体的中位数的估计量若总体为连续型且对称时,的中位数就是均值,即:该方法称为数学期望的顺序统计量估计法例:设灯泡寿命,为估计平均寿命,随机取,试用顺序统计量法估计.解:观测值的顺序统计量为:,所以#注:该方法的优点是不易受个别离群值的影响.②总体标准差的估计:设那么,总体的标准差可用样本极差
8、估计,即:为极差估计法。注:方法粗糙,当n较大时,远不如用S或估计的可靠.一.估计量的评选标准:由于 的随机