2.4.3 nemaresiphi Approximating

Singahlola okulinganiselwe esingakwenzanga noma esingenakukwenza. Izindlela ezimbili ezizuzisa kakhulu emithonjeni emikhulu yedatha zenzelwa ukuhlolwa kwemvelo nokulingana.

Eminye imibuzo ebalulekile yesayense nenqubomgomo iyabangela. Isibonelo, uyini umphumela womsebenzi wokuqeqesha umsebenzi ngezinkokhelo? Umcwaningi ozama ukuphendula lo mbuzo angase aqhathanise nemali engenayo yabantu ababhalisele ukuqeqeshwa kulabo abangenzanga. Kodwa kungakanani umahluko phakathi kwenkokhelo phakathi kwala maqembu kungenxa yokuqeqeshwa nokuthi kungakanani ngenxa yokungafani kokuphikisana phakathi kwabantu abhalisa nalabo abangenayo? Lo mbuzo onzima, futhi ungowokuhamba ngokuzenzakalelayo nedatha eyengeziwe. Ngamanye amazwi, ukukhathazeka mayelana nokungaboni ngaso linye okungafaniyo kuvela kungakhathaliseki ukuthi bangaki abasebenzi abakudatha yakho.

Ezimweni eziningi, indlela enamandla kakhulu yokulinganisa umphumela we-causal wezokwelapha ezithile, njengokuqeqeshwa komsebenzi, ukuqhuba ukuhlolwa okulawulwa ngokungahleliwe lapho umcwaningi ehambisa ngokungahambi ukwelashwa kwabanye abantu hhayi kwabanye. Ngizozinikela konke isahluko 4 ukuze kuvivinywa, ngakho-ke ngizogxila emaqhinga amabili angasetshenziswa ngemininingwane engahlosiwe. Isu sokuqala sincike ekubhekeni into eyenzekayo emhlabeni ukuthi ngezikhathi ezithile (noma cishe ngokungahleliwe) inikeza ukwelashwa kwabanye abantu hhayi kwabanye. Isu sesibili sincike ekubaleni idatha ngokungafani nokuzama ukuzama ukulandelana phakathi kwalabo abenza futhi abangazange bathole ukwelashwa.

I-skeptic ingase ifune ukuthi kokubili lezi zindlela kufanele kugwenywe ngoba zidinga ukucabanga okuqinile, ukucabanga okulukhuni ukuhlola nokuthi, ngokujwayelekile, kuvame ukuphulwa. Ngenkathi ngizwelana nalesi simangalo, ngicabanga ukuthi kuhamba kakhulu. Kuyiqiniso ukuthi kunzima ukwenza ngokulinganisela ukulinganisela kokulinganisa kwedatha engahlolwanga, kodwa angicabangi lokho kusho ukuthi akufanele sizame. Ngokuyinhloko, izindlela ezingezona zokuhlola zingasiza uma ukuvimbela kokungena ngemvume kukuvimbela ekuqhubeni ukuhlolwa noma uma izinkinga zokuziphatha zisho ukuthi awufuni ukuqhuba ukuhlolwa. Ngokuqhubekayo, izindlela ezingezona zokuhlola zingaba usizo uma ufuna ukusebenzisa ngokunenzuzo idatha esevele ikhona ukuze uhlele ukuhlolwa okulawulwa ngokungahleliwe.

Ngaphambi kokuqhubeka, kubalulekile ukuphawula ukuthi ukwenza izilinganiso zokuhlaziywa kungenye yezihloko eziyinkimbinkimbi kakhulu ekucwaningweni kwezenhlalakahle, futhi okungaholela ekuphikisaneni okukhulu nangokomzwelo. Ngalokhu okulandelayo, ngizokunikeza incazelo enhle yendlela ngayinye ukuze ngakhele intuition ngakho, ngizochaza ezinye izinselele ezivela lapho usebenzisa le ndlela. Iminye imininingwane mayelana nendlela ngayinye iyatholakala ezintweni ezisekupheleni kwalesi sahluko. Uma uhlela ukusebenzisa noma iyiphi yalezi zindlela ekucwaningweni kwakho, ngincoma kakhulu ukufunda enye yezincwadi eziningi ezinhle kakhulu kwi-causal inference (Imbens and Rubin 2015; Pearl 2009; Morgan and Winship 2014) .

Enye indlela yokwenza izilinganiso ze-causal kusuka kwedatha engekho yokuhlola ukubuka umcimbi oye wanikezela ukwelashwa kwabanye abantu hhayi kwabanye. Lezi zimo zibizwa ngokuthi izivivinyo zemvelo . Esinye sezibonelo ezicacile zokwenziwa kwemvelo kuvela ekucwaningweni kukaJoshua Angrist (1990) okulinganisa umphumela wezinsizakalo zempi ngokuthola imali. Phakathi nempi eVietnam, i-United States yanda ubukhulu bamasosha ayo ahlomile ngokusebenzisa uhlaka. Ukuze unqume ukuthi yiziphi izakhamuzi ezazobizwa ngokuthi zizosebenza, uhulumeni wase-US wayephethe i-lottery. Nsuku zonke zokuzalwa zabhalwa ephepheni, futhi, njengoba kuboniswe kumfanekiso 2.7, lezi ziqephu zephepha zikhethiwe ngesikhathi esisodwa ukuze kunqunywe ukuhlelwa kwamadoda amancane ukuzokhonza (abesifazane abasebasha babengenasifundo kuhlaka). Ngokusekelwe emiphumeleni, amadoda azalwa ngoSeptemba 14 abizwa kuqala, amadoda azalwa ngo-Ephreli 24 abizwa ngokuthi wesibili, njalonjalo. Ekugcineni, kule lottery, amadoda azalwa ngezinsuku ezingu-195 ahlukene aqoshwa, kuyilapho amadoda azalwa ezinsukwini ezingu-171 ayengekho.

Umdwebo 2.7: I-Congressman u-Alexander Pirnie (R-NY) udweba i-capsule yokuqala ye-Selective Service draft ngomhla kaDisemba 1, 1969. UJoshua Angrist (1990) wahlanganisa i-lottery ehleliwe ngemininingwane yokuthola imali evela ku-Social Security Administration ukulinganisa umphumela wemisebenzi yezempi kumholo. Lesi yisibonelo socwaningo ngokusebenzisa ukuhlolwa kwemvelo. Umthombo: US System Selective System (1969) / Wikimedia Commons .

Yize kungase kungabonakali ngokushesha, i-lottery ehleliwe ibaluleke kakhulu ekuhlolweni okulawulwa ngokungahleliwe: kuzo zombili izimo, abahlanganyeli banikezwa ngezikhathi ezithile ukuthola ukwelashwa. Ukuze ufunde umphumela walokhu ukwelashwa okungahleliwe, i-Angrist isebenzisa inqubo yesistimu ehlala njalo: i-US Social Security Administration, eqoqa ulwazi cishe wonke amaholo aseMelika kusukela emsebenzini. Ngokuhlanganisa ulwazi mayelana nokuthi ubani okhethiwe ngokukhethiwe ku-lottery ebhalisiwe ngemininingwane yokuthola imali eqoqwe kumarekhodi kahulumeni, u-Angrist waphetha ukuthi amaholo we-veterans ayengamaphesenti angama-15% kunemali engenayo ye-non-veteran.

Njengoba lesi sibonelo sibonisa, ngezinye izikhathi amandla ezombusazwe, ezombusazwe, noma ezemvelo anikeze ukwelashwa ngendlela engacwaningwa ngabacwaningi, futhi ngezinye izikhathi imiphumela yalezi zindlela zithathwa imithombo yamandla njalo. Lolu hlelo lokucwaninga lungabhalwa ngokulandelayo: \[\text{random (or as if random) variation} + \text{always-on data} = \text{natural experiment}\]

Ukuze sibonise leli qhinga eminyakeni yobudala, ake sicabangele isifundo sika-Alexandre Mas no-Enrico Moretti (2009) owazama ukulinganisa umphumela wokusebenza nabasebenza nabo abakhiqizayo emsebenzini wokukhiqiza. Ngaphambi kokubona imiphumela, kufanelekile ukukhomba ukuthi kunezinto okulindelekile ezingavumelani ukuthi ungaba nazo. Ngakolunye uhlangothi, ungalindela ukuthi ukusebenzisana nabalingani bokukhiqiza kuzoholela emsebenzini ukukhulisa umkhiqizo wakhe ngenxa yokucindezela kontanga. Noma, ngakolunye uhlangothi, ungalindela ukuthi ukuba nabalingane abasebenza kanzima bangase baholele isisebenzi ukuba siphume ngoba umsebenzi uzokwenziwa ngontanga yakhe noma kunjalo. Indlela ecacile yokutadisha imiphumela yontanga ekukhiqizeni kungaba ukuhlolwa okulawulwa ngokungahleliwe lapho abasebenzi behlelwa khona ngezikhathi ezithile ngokusebenza nabasebenzi bamazinga ahlukene okukhiqiza bese umkhiqizo ophumela kuwo ulinganiswa kuwo wonke umuntu. Kodwa-ke abacwaningi abalawuli ukuhlelwa kwezisebenzi kunoma yiliphi ibhizinisi langempela, ngakho uMas noMoretti kwakudingeka bathembele ekuhlolweni kwemvelo okuhilela amakhasimende esitolo.

Kule ndawo esitolo esithile, ngenxa yokuthi indlela yokuhlelwa kwenzelwe futhi indlela eyahamba ngayo, i-cashier ngayinye yayinezisebenzi ezihlukene ngezikhathi ezahlukene zosuku. Ngaphezu kwalokho, kule ndawo esitolo esithile, isabelo sabaniki besikhwama sasingahambisani nokukhiqizwa kontanga yabo noma ukuthi sasimatasa kangakanani esitolo. Ngamanye amazwi, nakuba ukuhlelwa kwama-cashashi akuzange kunqunywe i-lottery, kwakunjengokungathi izisebenzi ngezinye izikhathi zabekwa eceleni ukuba zisebenze ngeontanga eliphezulu (noma eliphansi) lokukhiqiza. Ngenhlanhla, lesi sitolo sasine-digital-age checkout system elandelela izinto umnikazi wekhompiyutha ngamunye owaskena ngazo zonke izikhathi. Kusuka kule datha yokungena kwe-log, iMas ne-Moretti bakwazi ukudala umkhiqizo oqondile, ngamunye, futhi njalo-njalo wokukhiqiza: inombolo yezinto eziskenwe ngomzuzwana. Ukuhlanganisa lezi zinto ezimbili-ukushintsha ngokwemvelo kokukhiqizwa kontanga nokukhiqiza njalo-uMas no-Moretti balinganisela ukuthi uma i-cashier isabelwe abasebenzisana nabo ababesebenza ngaphezulu kuka-10%, ukukhiqiza kwakhe kuzokwandisa ngo-1.5% . Ngaphezu kwalokho, basebenzisa ubukhulu bezinombolo zabo ukuze bahlole izinkinga ezimbili ezibalulekile: ukungafani kokusebenza kwalokhu (Ngokuba yiziphi izinhlobo zabasebenzi umthelela omkhulu?) Kanye nezinqubo ezithinta umphumela (Kungani ukuba nezingane ezikhiqizayo eziphezulu ziholela umkhiqizo ophezulu?). Sizobuyela kulezi zimpikiswano ezimbili ezibalulekile-ukuguquka kwemiphumela yokwelapha kanye nezinqubo-esahlukweni 4 lapho sixoxa ngokuhlola ngokuningiliziwe.

Ukukhiqiza ngezifundo ezimbili, ithebula le-2.3 lifingqa ezinye izifundo ezinesakhiwo esifanayo: besebenzisa umthombo wedatha njalo ukukala umphumela wokushintsha okungahleliwe. Ngokwenza njalo, abacwaningi basebenzisa amaqhinga amabili ahlukene okuthola ukuhlolwa kwemvelo, kokubili okungaba nokuthela. Abanye abacwaningi baqala ngomthombo wedatha njalo futhi babheka izenzakalo ezingahleliwe emhlabeni; abanye baqala umcimbi ongahleliwe emhlabeni futhi babheka imithombo yedatha ethatha umthelela wayo.

Engxoxweni kuze kube manje mayelana nokuhlolwa kwemvelo, ngishiye iphuzu elibalulekile: ukusuka kulokho uhlobo olunikezile kulokho okufunayo ngezinye izikhathi kungase kube lukhuni. Ake sibuyele esibonelweni se-Vietnam esisibonelo. Kulokhu, u-Angrist wayenesithakazelo ekuqhathaniseni umphumela wemisebenzi yezempi kumholo. Ngeshwa, inkonzo yezempi yayingabelwe ngezikhathi; kunalokho kwakubhalwe phansi okwakunikezwa ngezikhathi ezithile. Kodwa-ke, akuwona wonke umuntu owabhalwa wabhalwa (kunezinhlobo ezihlukahlukene zokukhululwa), futhi akuwona wonke umuntu owakhonza owabhalwa (abantu bangazivotela ukukhonza). Ngenxa yokuthi ukubhalwa kwanikezwa ngokungahleliwe, umcwaningi angalinganisa umphumela wokubhalwa kuwo wonke amadoda ekubhalweni. Kodwa u-Angrist wayengafuni ukwazi umphumela wokubhaliswa; wayefuna ukwazi umphumela wokukhonza empini. Ukuze wenze lokhu kulinganiselwa, noma kunjalo, ukucabanga okunye nokucindezeleka kuyadingeka. Okokuqala, abacwaningi kudingeka bacabange ukuthi indlela ewukuphela kokubhaliwe eyathinteka ekuzuzeni imali yilezi zamasosha, inkolelo ebizwa ngokuthi umkhawulo wokuqedwa . Lokhu kucabanga kungalungile uma, ngokwesibonelo, amadoda abhalwe phansi ahlala esikoleni isikhathi eside ukuze agweme ukukhonza noma uma abaqashi bengenakuthola ukuqasha amadoda abhalwe phansi. Ngokuvamile, umkhawulo wokukhishwa ukucabanga okubalulekile, futhi ngokuvamile kunzima ukuqinisekisa. Ngisho noma umkhawulo wokukhishwa ulungile, kusengenakwenzeka ukulinganisa umphumela wenkonzo kuwo wonke amadoda. Kunalokho, kubonakala ukuthi abacwaningi bangalinganisa kuphela umphumela esakhiweni esithile samadoda abizwa ngokuthi ama-compliers (amadoda angakhonza uma ehlelwa, kodwa angeke akhonze uma engabhalwanga) (Angrist, Imbens, and Rubin 1996) . Nokho, ama-compress ayengewona abantu abathintekayo. Qaphela ukuthi lezi zinkinga ziphakama ngisho naseceleni elihlanzekile lelot lottery. I-set of complications eqhubekayo ivela lapho ukwelashwa kungabelwe iloti yenyama. Isibonelo, ekutadisheni kukaMas no-Moretti ngabaqashi, imibuzo eyengeziwe iphakama mayelana nokucabangela ukuthi isabelo sontanga ngokuyinhloko sihleliwe. Uma lokhu kucatshangwa kwaphulwa ngokweqile, kungase kufakaze ukulinganisa kwabo. Ukuphetha, ukuhlolwa kwemvelo kungaba yindlela enamandla ekwenzeni izilinganiso ezivela emininingwaneni engeyona yokuhlola, futhi imithombo emikhulu yedatha ikwandisa ikhono lethu lokuzibandakanya ekuhlolweni kwemvelo uma kwenzeka. Kodwa-ke, cishe kuzodinga ukucabangela okukhulu-futhi ngezinye izikhathi ukucabanga okuqinile-ukuhamba kunoma imuphi uhlobo olunikeze ukulinganisela okufunayo.

Isu sesibili engingathanda ukukutshela mayelana nokwenza izilinganiso ezivela emininingwaneni engafani yokuhlola kuncike ekutheni zilungiswe ngokulinganisa idatha engahlolisi emzamweni we-akhawunti ngokungafani kokuphikisana phakathi kwalabo abenza futhi abangazange bathole ukwelashwa. Kukhona izinguquko ezinjalo eziseduze, kodwa ngizogxila kokunye okubizwa ngokuthi okufanako . Ngokulingana, umcwaningi ubheka idatha engahloliswanga ukuze adale amabilidi abantu abafana naye ngaphandle kokuthi omunye uthola ukwelashwa kanti omunye akakwenzi. Ngendlela yokufanisa, abacwaningi empeleni banquma futhi; okungukuthi, ukulahla amacala lapho kungekho mdlalo ocacile. Ngakho-ke, le ndlela izobizwa ngokunembile ngokufana nokufanisa nokukhipha izihlahla, kodwa ngizobambelela ngegama lesendabuko: ukufana.

Isibonelo esisodwa samandla amasu afanayo nemithombo enkulu yedatha engahlolisisi ivela ocwaningweni ngokuziphatha komthengi nguLiran Einav nozakwabo (2015) . Babenesithakazelo endalini eyenziwa eBay, futhi lapho bechaza umsebenzi wabo, ngizogxila emthethweni wezindalini zokuqala zendalini kwimiphumela yamadayimenti, njengenani lokuthengisa noma amathuba okuthengisa.

Indlela engafanele kakhulu yokulinganisa umphumela wokuqala kwentengo ngentengo yokuthengisa kuyoba ukumane ukubala intengo yokugcina yamayunivesithi ahlukene ngamanani okuqala. Le ndlela izoba kuhle uma ufuna ukubikezela intengo yokuthengisa enikezwe intengo yokuqala. Kodwa uma umbuzo wakho uphathelene nomphumela wamanani okuqala, le ndlela ngeke isebenze ngoba ayisekelwe ekuqhathaniseni okuhle; Izindleko ezinamanani aphansi okuqala zingase zihluke kakhulu kulabo abanamanani aphezulu okuqala (isib. bangase babe izinhlobo ezahlukene zezimpahla noma bahlanganise izinhlobo ezahlukene zabathengisi).

Uma usuvele uqaphela izinkinga ezingase zivele uma wenza izilinganiso ezivela emininingwaneni engahlosiwe, ungase weqe indlela engafanele futhi ucabange ukuqhuba ukuhlolwa kwensimu lapho ungathengisa into ethize-ithi, igalofu yegalofu isethi yemingcele yokudayiswa-ithi, ukuthunyelwa kwamahhala nokudayiswa kuvulelwe amasonto amabili-kodwa ngamanani okuqala angabelwe ngaso sonke isikhathi. Ngokuqhathanisa nemiphumela yemakethe ephumela, lolu cwaningo lwensimu lungahlinzeka ngokulinganisa okucacile komphumela wokuqala kwentengo ngentengo yokuthengisa. Kodwa lesi silinganiso sisebenza kuphela kumkhiqizo othize kanye nesethi yemingcele yokudayiswa. Imiphumela ingase ihluke, isibonelo, ngezinhlobo ezahlukene zemikhiqizo. Ngaphandle kwenkolelo eqinile, kunzima ukukhipha amandla kusuka kulolu cwaningo olulodwa kuya kuhla oluphelele lwezilingo ezingase ziqalwe. Ngaphezu kwalokho, ukuhlolwa kwensimu kuyabiza ngokwanele ukuthi kungenakukwazi ukuqhuba zonke izinhlobo ongafuna ukuzizama.

Ngokuphambene nezindlela ezingenalutho nezokuhlola, u-Einav nozakwabo bathatha indlela yesithathu: ukufanisa. Iqhinga eliyinhloko kumasu abo ukuthola izinto ezifana nokuhlolwa kwensimu okwenzekile ku-eBay. Isibonelo, isibalo se-2.8 sibonisa ezinye zezinhlawulo ezingu-31 zeqembu elilodwa legalufu-i-Taylormade Burner 09 Driver-edayiswa ngumdayisi ofanayo- "isabelomali." Nokho, lezi zihloko ezingu-31 zinemikhakha ehlukile, njengokuqala okuhlukile intengo, izinsuku zokuphela, nemali yokuthumela. Ngamanye amazwi, kunjengokuthi "i-budgetgolfer" iqhuba izivivinyo zabacwaningi.

Lezi zihloko ze-Taylormade Burner 09 Ukushayela okuthengiswa yi- "budgetgolfer" kuyisibonelo esisodwa sokuhlelwa kokufakwa kuhlu, lapho into efanayo edayiswa ngayo umdayisi ofanayo, kodwa njalo ngezici ezihlukile. Ngaphakathi kwezigxobo ezinkulu ze-eBay kunamagama ezinkulungwane ezilinganiselwe ezifakiwe ezibandakanya izigidi zokufakwa ohlwini. Ngakho-ke, kunokuqhathanisa intengo yokugcina yazo zonke izindalini ngezindleko zokuqala ezinikeziwe, u-Einav nozakwabo baqhathaniswa ngaphakathi kwamasethingi afanelanayo. Ukuze kuhlanganiswe imiphumela kusuka kokuqhathaniswa phakathi kwala makhulu ezinkulungwane zamasethingi afanelana, u-Einav nabalingani bakhe baphinde baveza intengo yokuqala kanye nentengo yokugcina ngokubaluleka kokubhekisela kwento ngayinye (isb., Intengo yayo yokuthengisa ejwayelekile). Isibonelo, uma i-Taylormade Burner 09 Driver enenani elilinganiselwa ku-$ 100 (ngokusekelwe ekuthengiseni kwayo), khona-ke intengo yokuqala ye $ 10 izoboniswa njenge-0.1 futhi inani lokugcina lika-$ 120 njenge-1.2.

Umdwebo 2.8: Isibonelo sesethi ehambelanisiwe. Leli yiyo efanayo igalofu ye-golf (i-Taylormade Burner 09 Driver) ethengiswa ngumuntu ofanayo ("ibhajethi"), kodwa ezinye zazo zenziwa ngaphansi kwezimo ezahlukene (isib. Amanani aqala ahlukene). Yenzelwe imvume evela ku- Einav et al. (2015) , isibalo 1b.

Khumbula ukuthi u-Einav nozakwabo babe nesithakazelo emvelweni wemiphumela yokuqala emiphumeleni. Okokuqala, basebenzisa ukuguqulwa okulinganiselwe ukulinganisela ukuthi amanani aphezulu okuqala ayanciphisa amathuba okudayiswa, nokuthi amanani aphezulu okuqala ayenyusa intengo yokuthengisa yokugcina (ngokomgomo ngokudayiswa). Ngabo ngokwabo, lezi zilinganiso-ezichaza ubudlelwane obufanayo futhi zenzelwe yonke imikhiqizo-akuzona zonke ezithakazelisayo. Khona-ke, u-Einav nozakwabo basebenzisa ubukhulu obukhulu bemininingwane yabo ukuze bakhe izilinganiso ezihlukahlukene ezicashile. Isibonelo, ngokulinganisa umphumela ngokwahlukana ngezintengo ezihlukahlukene zokuqala ezahlukahlukene, bathole ukuthi ubudlelwane obuphakathi kwentengo yokuqala kanye nentengo yokuthengisa akuyona yonlinear (umfanekiso 2.9). Ngokuyinhloko, ukuqala amanani phakathi kuka-0.05 no-0.85, intengo yokuqala ephethe umthelela omncane kakhulu entengo yokuthengiswa, okutholwe ukuthi kwakungaphuthelwa ngokuphelele ngokuhlaziywa kwabo kokuqala. Ngaphezu kwalokho, esikhundleni sokuphazamisa ngaphezu kwazo zonke izinto, u-Einav nosebenza nabo bacatshangelwa ukuthi umthelela wokuqala kwentengo yezinhlobo ezingu-23 zezinto (isb., Ukunikezwa kwemfuyo, i-electronics, kanye nememorabilia yezemidlalo) (umfanekiso 2.10). Lezi zilinganiso zibonisa ukuthi izinto eziningi ezihlukile-njengemikhumbi yokuqala-memorabilia inomthelela omncane kumathuba okudayiswa kanye nomthelela omkhulu emanani okuthengisa okugcina. Ngaphezu kwalokho, ukuze uthole izinto eziningi ezihambelanayo-njenge-DVD-intengo yokuqala ayifuni nomthelela kumanani okugcina. Ngamanye amazwi, isilinganiso esihlanganisa imiphumela kusuka kwizigaba ezingu-23 ezahlukene zezinto kufihla umehluko obalulekile phakathi kwalezi zinto.

Umdwebo 2.9: Intengo yokuqala phakathi kweyendali kanye namathuba okudayiswa (a) nentengo yokuthengisa (b). Kukhona ubuhlobo obuncane phakathi kokuqala kwentengo namathuba okudayiswa, kodwa ubudlelwane obungafani phakathi kokuqala kwentengo nentengo yokuthengisa; ngokuqala amanani phakathi kuka-0.05 no-0.85, intengo yokuqala inegalelo elincane kakhulu entengo yokuthengisa. Kuzo zombili izimo, ubudlelwane ngokuyinhloko buzimele ngokubaluleka kwento. Ishintshwe ku- Einav et al. (2015) , izibalo 4a no 4b.

Umdwebo 2.10: Kulinganiswa kusuka esigabeni ngasinye sezinto; iphashazi eliqinile ukulinganisa kwazo zonke izigaba ezihlangene ndawonye (Einav et al. 2015) . Lezi zilinganiso zibonisa ukuthi ngezinto eziningi ezihlukile-njengememorabilia-intengo yokuqala inomthelela omncane kumathuba okudayiswa ( \(x\) -axis) nomphumela omkhulu ekuthengisweni kwentengo yokugcina ( \(y\) -axis). Ishintshwe ku- Einav et al. (2015) , isibalo 8.

Ngisho noma ungekho ikakhulukazi unentshisekelo endalini e-eBay, kufanele uhloniphe indlela isibalo esingu-2.9 nesibalo esingu-2.10 esinikeza ukuqonda okucebile kwe-eBay kunezilinganiso ezilula ezichaza ubuhlobo obuhambisanayo futhi zihlanganise imikhakha eminingi yezinto. Ngaphezu kwalokho, nakuba kungase kube ngokwesayensi ukukhiqiza izilinganiso ezicashile kakhulu zokuhlolwa kwensimu, izindleko zingenza lokho kuhlolwa kungenakwenzeka.

Njengokuhlolwa kwezemvelo, kunezindlela eziningi ezifanelana nazo zingaholela ezilinganisweni ezimbi. Ngicabanga ukuthi ukukhathazeka okukhulu kakhulu ngokulinganisa okulinganayo kungukuthi banganakwa yizinto ezingasetshenziswanga ngokufanayo. Isibonelo, emiphumeleni yabo eyinhloko, u-Einav nozakwabo benza okufanayo ngokuhambisana nezici ezine: inombolo ye-ID yomthengisi, isigaba sento, isihloko sento, nombhalo ongenhla. Uma izinto zihlukile ngezindlela ezingazange zisetshenziselwe ukufanisa, khona-ke lokhu kungenza ukufaniswa okungafanele. Isibonelo, uma i-"budgetgolfer" inciphisa izintengo ze-Taylormade Burner 09 Driver ebusika (lapho amaqembu egalufu engatholakali kangako), khona-ke kungase kubonakale ukuthi amanani aphansi okuqala aholela ekunciphiseni amanani okugcina, kanti empeleni lokhu kungaba yi-artifact ukuhlukahluka kwonyaka ngokufunwa. Enye indlela yokubhekana nalesi sikhathazo izama izinhlobo eziningi ezihambisanayo. Isibonelo, u-Einav nozakwabo baphinda bahlaziya ukuhlaziywa kwabo ngenkathi behlukana nefasitela lesikhathi esetshenziselwa ukulinganisa (ukulinganisa okufakiwe kubandakanya izinto ezithengiswa phakathi nonyaka owodwa, kungakapheli inyanga eyodwa, futhi ngokucabangela). Ngenhlanhla, bathole imiphumela efanayo kuwo wonke amafasitela wesikhathi. Okunye ukukhathazeka okuhambisana nokuvela okuvela ekuchazeni. Ukulinganisela kokufana kufaka isicelo kuphela kumininingwane ehambelanisiwe; azisebenzi ezinkantolo ezingenakufaniswa. Isibonelo, ngokunciphisa ucwaningo lwabo ezintweni ezazinokufakwa ohlwini okuningi, u-Einav nozakwabo bagxila kubathengisi abaqeqeshiwe nabaqeqeshiwe. Ngakho-ke, lapho uhumusha lezi ziqhathaniso kumele sikhumbule ukuthi zisebenza kuphela kule subset ye-eBay.

Ukuqhathanisa kuyisisindo esinamandla sokuthola ukuqhathaniswa okungafanele emininingeni engekho yokuhlola. Kwabaningi ososayensi bezenhlalakahle, ukulinganisa uzizwa okwesibili-okungcono kakhulu ekuhlolweni, kodwa lokho kuyinkolelo engabuyekezwa, kancane. Ukuqhathaniswa kwedatha enkulu kungase kube ngcono kunezinombolo ezincane zokuhlolwa kwensimu uma (1) imiphumela ye-heterogeneity ibalulekile futhi (2) iziguquguquki ezibalulekile ezidingekayo zokufananisa zilinganisiwe. Ithebula 2.4 linikeza ezinye izibonelo zendlela ukufaniswa kungasetshenziswa ngayo nemithombo emikhulu yedatha.

Ekuphetheni, ukulinganisa imiphumela ye-causal kusuka kwedatha engafani yokuhlola kunzima, kodwa ukuhambisana nokuhlolwa okusemvelo nokulungiswa kwezibalo (isib. Ukufanisa) kungasetshenziswa. Kwezinye izimo, lezi zindlela zingahamba kabi, kodwa uma zisetshenziswe ngokucophelela, lezi zindlela zingaba usizo ekusetshenzisweni kokuhlola engikuchazayo esahlukweni 4. Ngaphezu kwalokho, lezi zindlela ezimbili zibonakala sengathi zizuze ekukhuleni njalo- ku, amasistimu amadatha amakhulu.