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1、參數(shù)估計(jì)(復(fù)習(xí))通過(guò)對(duì)樣本的處理,對(duì)總體的未知參數(shù)(如:數(shù)學(xué)期望、方差等)作出較好的估計(jì).一.點(diǎn)估計(jì)量的求法:1.矩法:①參數(shù):設(shè)或稱為參數(shù)②點(diǎn)估計(jì):設(shè)參數(shù)未知?jiǎng)t構(gòu)造統(tǒng)計(jì)量去估計(jì)稱為的估計(jì)量,為的估計(jì)值,估計(jì)量、估計(jì)值統(tǒng)稱估計(jì)。這種對(duì)未知參數(shù)的定值估計(jì)稱為點(diǎn)估計(jì)。③矩法:用樣本矩一般步驟是:設(shè),其中參數(shù)待估.(i),計(jì)算;(ii)由=或即:即:有個(gè)估計(jì)量例:(P110)設(shè)=,求otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiangxi,andDirectorofthenewOff
2、iceinJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,DirectorofNingxiaCountyparty
3、CommitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand19。解:由于=;又=則由#2.極大似然法設(shè),其中未知,則:,得的聯(lián)合分布稱為似然函數(shù)解題方法:將似然函數(shù)取對(duì)數(shù),有:對(duì)上式求偏導(dǎo),并令由k元方程組(似然方程組)求得例:(P118)設(shè),概率密度為=,,試求的極大似然估計(jì).otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiangxi,andDirectorofthenewOffice
4、inJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,DirectorofNingxiaCountypartyCom
5、mitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand19解:的似然函數(shù)為兩邊取對(duì)數(shù),得:似然方程為即:的極大似然估計(jì)量為#例:(P120)設(shè)在上服從均勻分布,,求的極大似然估計(jì)量.解:的分布密度為:∴ 似然函數(shù)為:顯然對(duì)無(wú)法利用令偏導(dǎo)數(shù)等于零的方法求駐點(diǎn),使得在某點(diǎn)處有:事實(shí)上:由,即:所以在上,為的最大值.故得的極大似然估計(jì)量為:#otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiang
6、xi,andDirectorofthenewOfficeinJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,Dir
7、ectorofNingxiaCountypartyCommitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand193.順序統(tǒng)計(jì)量法:①總體均值的估計(jì):設(shè) 記中位數(shù)可用:作為總體的中位數(shù)的估計(jì)量若總體為連續(xù)型且對(duì)稱時(shí),的中位數(shù)就是均值,即:該方法稱為數(shù)學(xué)期望的順序統(tǒng)計(jì)量估計(jì)法例:設(shè)燈泡壽命,為估計(jì)平均壽命,隨機(jī)取,試用順序統(tǒng)計(jì)量法估計(jì).解:觀測(cè)值的順序統(tǒng)計(jì)量為:,所以#注:該方法的優(yōu)點(diǎn)是不易受個(gè)別離群值的影響.②總體標(biāo)準(zhǔn)差的估計(jì):設(shè)那么,總體的標(biāo)準(zhǔn)差可用樣本極差
8、估計(jì),即:為極差估計(jì)法。注:方法粗糙,當(dāng)n較大時(shí),遠(yuǎn)不如用S或估計(jì)的可靠.一.估計(jì)量的評(píng)選標(biāo)準(zhǔn):由于 的隨機(jī)