2.4.3.1 tijaabo Dabiiciga ah

Tijaabo Dabiiciga ah ka faa'iidaystaan ​​dhacdooyinka random adduunka. dhacdo random + had-on nidaamka xogta = tijaabo dabiiciga ah

Furaha tijaabo gacanta ku nasiibin awood barbardhigo qurux randomization ah. Si kastaba ha ahaatee, mararka qaarkood wax ka dhaca dunida in muhiimad ku meelaynayaa dadka kala sooc lahayn ama ku dhowaad kala sooc lahayn in daaweyn kala duwan. Mid ka mid ah tusaalooyin cad ee istaraatijiyadda isticmaalka tijaabo dabiiciga ah waxay ka timaadaa cilmi of Angrist (1990) in cabiraya saameynta adeegyada military on dakhliga.

Intii lagu guda jiray dagaalka ee Vietnam, Maraykanka kordhay size ee ciidamada qalabka sida iyada oo qabyo ah. Si aad u go'aansato muwaadiniinta waxaa loogu yeedhi lahaa geli jiray, dawladda Maraykanka lagu qabtay bakhtiyaa. dhalashada kasta waxaa wakiil on warqad, iyo waraaqaha, kuwaas oo la dhigay in weel galaas ballaaran. Sida ku cad Jaantuska 2.5, kuwaas oo geedo of warqad la dajin lahaa weel hal mar si loo ogaado si ah in ragga dhallinyarada ah waxaa loogu yeedhi lahaa in ay u adeegaan (haweenka dhallinyarada ah laguma soo rogin qabyada ah). Iyada oo ku saleysan natiijooyinka, oo nin u dhashay on September 14 ayaa marka hore la odhan jiray, oo nin u dhashay on April 24 ayaa lagu magacaabay labaad, iyo wixii la mid ah. Ugu dambayntii, in bakhtiyaa this, nin ku dhashay 195 maalmood oo kala duwan ayaa ugu baaqay in ay adeeg halka nin ku dhashay 171 maalmood uma uu yeedhin.

Jaantuska 2.5: Congressman Alexander Pirnie (R-NY) barbaro kaabsal ugu horeysay ee qabyada ah Selective Service on 1 December, 1969 Joshua Angrist (1990) marka la isku daro baqtiyaanasiibka qabyada ah la xogta dakhliga ka Social Security Administration in la qiyaaso saamaynta adeega ciidamada dakhliga. Tani waa tusaale ka mid ah cilmi-baaris la isticmaalayo tijaabo dabiiciga ah. Source: Wikimedia Commons

Inkasta oo aan laga yaabaa in isla markiiba muuqata, bakhtiyaa qabyo ah ayaa la mid ah muhiim u ah tijaabo nasiibin gacanta, in labada xaaladaha ka qaybgalayaasha waxa aan kala sooc lahayn loo xilsaaray si ay u helaan daaweyn ah. In the case of bakhtiyaa qabyada ah, haddii aynu nahay xiiso barashada ku saabsan saamaynta qabyo-qalmitaanka iyo ciidamada dakhliga suuqa shaqada ku xiga, waxaan is barbardhigi kartaa natiijooyinka dadka dhalashada ahaayeen hoose xadka bakhtiyaanasiibka (tusaale ahaan, September 14, April 24, iwm) la natiijooyinka ee dadka dhalashada ahaayeen ka dib markii ay xadka ka (tusaale ahaan, February 20, December 2, iwm).

Marka la eego in daaweyn this ee la qoray ayaa lagu kala sooc lahayn loo xilsaaray, waxaan ka dibna loo qiyaaso kartaa saamaynta daaweyn this for natiijada kasta oo uu soo qiyaasay. Tusaale ahaan, Angrist (1990) marka la isku daro macluumaadka ku saabsan oo loo xushay in qabyada ah la xogta dakhliga la ururiyey by Social Security Administration in lagu gabagabeeyo in dakhliga ee veterans cad ahaayeen wax ka yar ee dakhliga ee u dhigma non-ruug oo ku saabsan 15% . cilmi kale isticmaashay trick la mid ah sidoo kale. Tusaale ahaan, Conley and Heerwig (2011) marka la isku daro macluumaadka ku saabsan oo loo xushay in qabyada ah la xogta qoyska laga soo ururiyey Survey 2000 Census iyo 2005 American Community iyo ogaaday in si dheer ka dib qabyada ah, waxaa jiray saamayn muddo dheer ah in yar oo ka mid ah ciidamada kala duwan ee natiijooyinka sida muddada guryaha (lahaanshaha kasoo horjeeddo kiraysanayso) iyo xasilooni la deggan yahay (suurtagalnimada of isagoo u dhaqaaqay in shantii sano ee hore).

Tusaale ahaan this muujinayaa, mararka qaarkood ciidamada bulsho, siyaasadeed, ama dabiiciga abuuro tijaabo ama meel u dhow-tijaabo oo la Taliyuhu kartaa cilmi. Inta badan tijaabo dabiiciga ah waa habka ugu fiican in la qiyaaso xidhiidhada sababta-iyo-dhaqan goobaha ay ma aha anshax ama wax ku ool ah si ay u ordaan tijaabo nasiibin gacanta. Iyagu waa istiraatiijiyad muhiim ah oo ay ogaadeen in lala barbardhigo cadaalad ah in xogta aan tijaabo. Qorshaha cilmi baadhista Tan waxaa lagu soo koobi karaa by isla'eg this:

\ [\ text {random (ama sida haddii random) dhacdo} + \ text {had-ku il xogta} = \ text {tijaabo dabiiciga ah} \ qquad (2.1) \]

Si kastaba ha ahaatee, falanqaynta ee tijaabo dabiiciga ah waxay noqon kartaa arrin adag. Tusaale ahaan, in ay dhacdo qabyo Vietnam ah, qof kasta oo aan oo ahaa qabyo-u qalma, islamarkaana (waxaa ku jiray noocyo kala duwan oo ka reeban). Oo, waqti isku mid ah, dadka qaar oo aan qabyada-u qalma si iskeed ah u bixinayno adeegidda. Waxa ay ahayd sida haddii lagu tijaabiyey caafimaad ee daroogada cusub, dadka qaar in kooxda daaweynta ma qaataan daawo iyo qaar ka mid ah dadka in kooxda ay gacanta ku bartey helay daroogada. Dhibaatadaan, wuxuu u yeedhay laba ajligeeda dhinac, sidoo kale dhibaatooyin kale oo badan waxa lagu sharaxay si faahfaahsan weyn ee qaar ka mid ah akhrinta talinayaa dhamaadka cutubkan.

istaraatijiyad ee ka faa'iidaysanaya si dabiici ah ka dhaca howsha random horreeyaa da'da digital, laakiin baahsanaanta xogta weyn ka dhigaysa istaraatijiyad this inta badan ka sahlan in ay isticmaalaan. Marka aad ay ogaadaan daaweyn qaar ka mid ah ayaa lagu kala sooc lahayn loo xilsaaray, ilaha xogta weyn ku siin karaan macluumaadka natiijada in aad u baahan tahay si ay u barbar dhigaan natiijada dadka xaaladaha daaweynta iyo gacanta ku. Tusaale ahaan, in uu waxbarasho ee saamaynta adeegga qabyada ah iyo ciidamada, Angrist dhigay isticmaalka xogta dakhliga ka Social Security Administration, aan xogta natiijada this, inuu waxbarasho lahaa suuragal ah in aan. Xaaladdan oo kale, Social Security Administration waa isha macluumaadka weyn ee had iyo jeer-on. Sida ilo xog iyo aad u badan si toos ah u soo ururiyey jiraan, aannu yeelan doono xogta natiijada ka badan in loo cabbiro karo saameynta isbedelka abuuray by kala duwanaanshaha exogenous.

Si aad u muujiso qorshahan in da'da digital, aynu fiirsan Mas iyo Moretti ee (2009) cilmi-baaris xarrago on saamaynta facooda on saarka. Inkasta oo dushiisa waxaa eegto laga yaabaa in uu ka duwan yahay waxbarasho Angrist ee ku saabsan saamaynta Qabyo Vietnam ah, in qaab dhismeedka labada ay raacaan hannaanka ee Equatorial. 2.1.

Mas iyo Moretti qiyaasay sida facooda saamayn wax soo saarka shaqaalaha. Dhinaca mid, isagoo isku faca adag ka shaqeeya oo laga yaabo keeni shaqaalaha si ay u kordhiyaan wax soo saarka sababtoo ah cadaadiska delegan. Or, ayaa dhanka kale, faca a shaqeeya adag u keeni karaa shaqaalaha kale inay raajin off xitaa more. Habka ugu cad inaad wax ka barato saamaynta faca on saarka noqon tijaabo nasiibin gacanta meesha shaqaalaha waxaa lagu kala sooc lahayn loo xilsaaray in ay xilliyo la shaqeeya heerar kala duwan soo saarka iyo wax soo saarka markaas keentay ayaa lagu qiyaasay qof walba uu doonaynin. Cilmi, si kastaba ha ahaatee, ma xakameeyo jadwalka shaqaalaha ganacsiga dhabta kasta, iyo si Mas iyo Moretti lahaa in ay ku tiirsan yihiin tijaabo dabiici ah oo ka dhacay suuqa weyn a.

Sida Equatorial. 2.1, ay baadhitaan lahaa laba qaybood. First, ay abuse ka soo nidaamka magalka supermarket loo isticmaalo in ay leeyihiin a saxda ah, shaqsi, oo had iyo jeer-on qiyaas ee wax soo saarka, tirada alaabta iskaan per labaad. Oo, labaad, sababtoo ah sida jadwalka wixii la sameeyey ee supermarket this, waxay leeyihiin meel u dhow Halabuurka kadiska ah ee facooda. In si kale loo dhigo, inkastoo jadwalka ee dhowr khasnaji aan la go'aamiyey by bakhtiyaa, waxay ahayd muhiimad random. In dhaqanka, kalsoonida aan ku leenahay tijaabo dabiiciga ah inta badan ku taagnaa plausibility ee this "as-haddii" sheegasho random. Qaadashada faa'iidaystaan ​​this duwanaansho random, Mas iyo Moretti ogaaday in la facooda soo saarka sare shaqeeya kordhiyaa wax soo saarka. Dheeraad ah, Mas iyo Moretti isticmaalo xajmiga iyo qaninimo ay dataset ay ka gudbaan ku qiimaysay ee Jidka-iyo-saamaynta ay ku sahamiyaan laba arrimood more muhiim ah oo khiyaano: heterogeneity of saamayn this (kaas oo noocyada kala duwan ee shaqaalaha waa saamaynta weyn) iyo hab ka dambeeya saamaynta (maxaad isagoo facooda soo saarka sare u wadin inuu soo saarka sare). Waxaan ku soo laaban doona labadan muhiim arrimaha-heterogeneity of saamaynta iyo hab-Cutubka 5 daaweynta marka aynu ka hadlayno tijaabo si faahfaahsan.

Guud daraasaadka ku saabsan saamaynta Qabyo Vietnam oo ku saabsan dakhliga iyo daraasadda of saamaynta facooda on saarka, Shaxda 2.3 koobayaa daraasado kale in ay leeyihiin tani qaab-dhismeedka isla saxda ah: isticmaalaya ah had iyo jeer-on il xogta si loo cabbiro saameynta ay dhacdo qaar ka mid ah . Sida Shaxda 2.3 caddeeyo, tijaabo dabiici ah meel kasta waa haddii aad kaliya ogaado sida ay u eegaan iyaga u.

In dhaqanka, cilmi isticmaasho laba xeelado kala duwan ee loo helo tijaabo dabiiciga ah, labadaas arrimood oo aad noqon kartaa barwaaqo ah. Qaar ka mid ah cilmibaadhayaasha la bilaabi isha had-on xogta iyo raadi dhacdooyinka random adduunka; kuwa kale ku bilaw dhacdooyinka random adduunka iyo raadiyo ilaha xogta in ay qabsadaan ay saameyn. Ugu dambeyntii, aragto in xoogga tijaabo dabiiciga ah ma ka yimaado koobaa ee falanqaynta tirakoobka, laakiin daryeelka in ay ogaadeen barbardhigo cadaalad abuuray by shil nasiib taariikhda.