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1、參數(shù)估計(復習)通過對樣本的處理,對總體的未知參數(shù)(如:數(shù)學期望、方差等)作出較好的估計.一.點估計量的求法:1.矩法:①參數(shù):設(shè)或稱為參數(shù)②點估計:設(shè)參數(shù)未知則構(gòu)造統(tǒng)計量去估計稱為的估計量,為的估計值,估計量、估計值統(tǒng)稱估計。這種對未知參數(shù)的定值估計稱為點估計。③矩法:用樣本矩一般步驟是:設(shè),其中參數(shù)待估.(i),計算;(ii)由=或即:即:有個估計量例:(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)取對數(shù),有:對上式求偏導,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.otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiangxi,andDirectorofthenewOffice
4、inJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,DirectorofNingxiaCountypartyCom
5、mitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand19解:的似然函數(shù)為兩邊取對數(shù),得:似然方程為即:的極大似然估計量為#例:(P120)設(shè)在上服從均勻分布,,求的極大似然估計量.解:的分布密度為:∴ 似然函數(shù)為:顯然對無法利用令偏導數(shù)等于零的方法求駐點,使得在某點處有:事實上:由,即:所以在上,為的最大值.故得的極大似然估計量為:#otherstaffoftheCentre.Duringthewar,ZhuwastransferredbacktoJiang
6、xi,andDirectorofthenewOfficeinJingdezhen,JiangxiCommitteeSecretary.Startingin1939servedasrecorderoftheWestNorthOrganization,SecretaryoftheSpecialCommitteeAfterthevictoryofthelongMarch,hehasbeentheNorthwestOfficeoftheFederationofStateenterprisesMinister,ShenmufuguSARmissions,Dir
7、ectorofNingxiaCountypartyCommitteeSecretaryandrecorderoftheCountypartyCommitteeSecretary,Ministersand193.順序統(tǒng)計量法:①總體均值的估計:設(shè) 記中位數(shù)可用:作為總體的中位數(shù)的估計量若總體為連續(xù)型且對稱時,的中位數(shù)就是均值,即:該方法稱為數(shù)學期望的順序統(tǒng)計量估計法例:設(shè)燈泡壽命,為估計平均壽命,隨機取,試用順序統(tǒng)計量法估計.解:觀測值的順序統(tǒng)計量為:,所以#注:該方法的優(yōu)點是不易受個別離群值的影響.②總體標準差的估計:設(shè)那么,總體的標準差可用樣本極差
8、估計,即:為極差估計法。注:方法粗糙,當n較大時,遠不如用S或估計的可靠.一.估計量的評選標準:由于 的隨機