2.4.3 imifuniselo Approximating

Siyakwazi ukulinganisa okulinganayo esingenako okanye esingenako ukwenza. Iindlela ezimbini ezibaluleka ngokukodwa kwimithombo emikhulu yedata zizama ukuhlola kunye nokulingana.

Eminye imibuzo ebalulekileyo yenzululwazi nemigaqo-nkqubo iyabangela. Umzekelo, yintoni umphumo wenkqubo yoqeqesho lomsebenzi kwimvuzo? Umphandi ozama ukuphendula lo mbuzo unokuthelekisa umvuzo wabantu ababhalisele ukuqeqeshwa kwabo bangenalo. Kodwa ingaba phi nawuphi na umehluko wemvuzo phakathi kwala maqela ngenxa yoqeqesho kunye nokuba lukhulu kangakanani ngenxa yokungafani koluphakathi phakathi kwabantu abhalisa kunye nalabo abangenayo? Lo ngumbuzo onzima, kwaye ngowona ongahambi ngokuzenzekelayo ngolwazi olungaphezulu. Ngamanye amazwi, inkxalabo malunga nokungafani okungafaniyo kuvela kungakhathaliseki ukuba bangaphi abasebenzi abakukho idatha yakho.

Kwiimeko ezininzi, indlela enamandla kakhulu yokuqikelela umphumo wonyango othile, njengokuqeqeshwa komsebenzi, ukuqhuba uvavanyo olulawulwa ngokungahleliwe apho umphandi unika ngokukhawuleza unyango kwabanye abantu ngaphandle kwabanye. Ndiza kunika yonke isahluko 4 ukuvavanya, ngoko ndiza kugxila kwiindlela ezimbini ezingasetyenziselwa idatha engeyiyo yokulinga. Isicwangciso sokuqala sincike ekukhangekeni into eyenzekayo kwihlabathi elandelelanayo (okanye ngokukhawuleza ngokukhawuleza) inikezela unyango kwabanye abantu ngaphandle kwabanye. Isicwangciso sesibini sixhomekeke kwi-statistically ukulungelelanisa idatha engeyiyo yokuzama ukuzama ukuxubusha ukungaboni ngaso linye phakathi kwabo benzayo kwaye abazange bamkele unyango.

I-skeptic inokuba ibango lokuba zombini ezi zicwangciso kufuneka ziphetshwe ngenxa yokuba zifuna ukucinga okuqinileyo, iingcamango ezinzima ukuvavanya kwaye, ngokuqhelekileyo, zihlala ziphulwa. Nangona ndiba novelwano kule bango, ndicinga ukuba kuhamba kakhulu. Ngokuqinisekileyo ukuba kunzima ukwenza uqikelelo lweengxelo zeengxelo ezingezizo, kodwa andicinga ukuba oko akumele sizame. Ngokukodwa, iindlela ezingezizo zovavanyo zinokukunceda ukuba imithintelo yokungena kwimiqobo ikuthintele ekubeni uqhube uvavanyo okanye ukuba imithintelo yokuziphatha ithetha ukuba awufuni ukuqhuba uvavanyo. Ukuqhubela phambili, iindlela ezingezizo zovavanyo zinokukunceda ukuba ufuna ukusebenzisa i-data ekhoyo kakade ukwenzela ukuyila ukuhlolwa okungalawulwa ngokungahleliwe.

Ngaphambi kokuba kuqhutywe phambili, kuyafaneleka ukuba uqaphele ukuba ukuqikelelwa kwezinto ezinokubaluleka kunomnye wezihloko eziyinkimbinkimbi kwiphando loluntu, kwaye enye inokukhokelela kwingxabano enzulu kunye nengqondo. Ngalolu hlobo lulandelayo, ndiya kunika inkcazo enethemba nganye kwendlela yokwakha intuition malunga nayo, ngoko ndiza kuchaza ezinye zeengxaki ezivela xa usebenzisa le ndlela. Iinkcukacha ezongezelelweyo malunga nendlela nganye zifumaneka kwizinto ekupheleni kwesi sahluko. Ukuba uceba ukusebenzisa le ndlela kuphando lwakho, ndincoma kakhulu ukufunda enye yeencwadi ezilungileyo kakhulu kwi-causal inference (Imbens and Rubin 2015; Pearl 2009; Morgan and Winship 2014) .

Enye indlela yokwenza uqikelelo lwe-causal kwi-data engeyiyo yokuhlola ukujonga isiganeko esiye sabela ngonyango abanye abantu kungekhona kwabanye. Ezi meko zibizwa ngokuba yizilingo zemvelo . Esinye sezibonelo ezicacileyo zolu vavanyo lwendalo luvela kuphando lukaJoshua Angrist (1990) olulinganisa umphumo weenkonzo zemikhosi kwimbuyekezo. Ngexesha lemfazwe eVietnam, iUnited States yanda ubungakanani bemikhosi yayo yokuxhoba ngokuqulunqa. Ukuze unqume ukuba ngubani na oza kuthiwa abe yinkonzo, urhulumente wase-US ubambe i-lottery. Yonke imihla yokuzalwa yabhalwa kwisiqephu sephepha, kwaye, njengoko kuboniswe kumfanekiso 2.7, ezi zicatshulwa zephepha zikhethiwe enye ngexesha ukwenzela ukuba zichane umyalelo apho amadoda amancinci aya kubizwa khona ukuba asebenze kwidrafti). Ngokusekelwe kwiziphumo, amadoda azalwa ngoSeptemba 14 abizwe kuqala, amadoda azalwa ngo-Ephreli 24 abizwa ngokuba ngowesibili, njalo njalo. Ekugqibeleni, kule lottery, amadoda azalwa ngemihla engama-195 eyahlukileyo yaqulunqwa, ngoxa amadoda azalwe kwiintsuku eziyi-171 ayengekho.

Umzekeliso 2.7: I-Congressman Alexander Pirnie (R-NY) udweba i-capsule yokuqala kwi-Yunyulo yoNyulo lweeNkonzo ngomhla kaDisemba 1, 1969. UJoshua Angrist (1990) wadibanisa i-lottery yenkcazelo kunye nemali yokufumana i-Social Security Administration ukuqikelela umphumo wenkonzo yempi kwimali. Lo ngumzekelo wophando usebenzisa uvavanyo lwendalo. Umthombo: I-US Selective Service System (1969) / Wikimedia Commons .

Nangona kungenakukubonakala ngokukhawuleza, i-lottery iqulunqwe ngokubaluleka ngokubanzi kumvavanyo olawulwa ngokungahleliwe: kuzo zombini iimeko, abathathi-nxaxheba banikwa ngokulandelelana ukuba bafumane unyango. Ukuze ufunde isiphumo salolu unyango olungenamsebenzi, i-Angrist yayisebenzise indlela yokugcina idatha enkulu: Ulawulo lwezoKhuseleko lwaseNtlalweni yase-US, oluqokelela ulwazi malunga nayo yonke imali yaseMelika evela kwingqesho. Ngokudibanisa ulwazi malunga nokuba ngubani okhethwe ngokukhethiweyo kwi-lottery ebhaliweyo kunye nedatha yokufumana eyayiqokelelwa kwiirekhodi zolawulo, u-Angrist wagqiba ukuba i-earnings ye-veterans yayingama-15% ngaphantsi komvuzo we-non-veteran.

Njengoko lo mzekelo ubonisa, ngamanye amaxesha inzululuntu, ezopolitiko, okanye imvelo yenzelwa unyango ngendlela echaneke ngayo ngabaphandi, kwaye ngamanye amaxesha iziphumo zonyango zifakwe kwiindawo ezininzi zedatha. Isicwangciso sophando singatshwankathela ngolu hlobo lulandelayo: \[\text{random (or as if random) variation} + \text{always-on data} = \text{natural experiment}\]

Ukuzekelisa esi sicwangciso kwixesha ledijithali, makhe sihlolisise i-Alexandre Mas kunye no-Enrico Moretti (2009) ozama ukulinganisa umphumo wokusebenza kunye noogxa abasebenza ngokuvelisa kwimveliso yomsebenzi. Ngaphambi kokubona iziphumo, kubalulekile ukuba ukhombise ukuba kukho ukulindela okungafaniyo. Ngakolunye uhlangothi, unokulindela ukuba ukusebenzisana nabalingane abavelisayo kuya kubangela ukuba umsebenzi akhulise umveliso wakhe ngenxa yoxinzelelo lwabaontanga. Okanye, ngakolunye uhlangothi, unokulindela ukuba oontanga abanomsebenzi onzima bangakhokelela umsebenzi ukuba alahleke ngenxa yokuba umsebenzi uya kwenziwa ngontanga yakhe. Indlela ecacileyo yokufunda iziphumo zontanga kwimveliso iya kuba yindlela elawulwa ngokungahleliwe apho abasebenzi banokunikezelwa ngokuzenzekelayo ukuhamba kunye nabasebenzi bamazinga ahlukeneyo okuvelisa kwaye umphumo oveliswayo ulinganiswa kuwo wonke umntu. Abaphandi, nangona kunjalo, abalawulwa kwishedyuli yabasebenzi kuyo nayiphi na ishishini lokwenene, kwaye ngoko uMas no-Moretti babefanele bathembele kwindlela eyenziwa yile mveliso eyenza abashibi kwivenkile.

Kule shishini elithile, ngenxa yendlela yokwenza ishedyuli yenziwe kunye nendlela eya kutshintsha ngayo, umqeshi ngamnye wasebambisene nabo abahlukeneyo ngamaxesha ahlukeneyo emini. Ukongezelela, kule shishini elithile, isabelo sabasemagunyeni asihambisani nokuveliswa kweontanga okanye ukuba zixakeke kangakanani ivenkile. Ngamanye amazwi, nangona ukucwangciswa kwabaqeshi bekungakhange kunqunywe ilokotri, kwakunjengokuthi ngabasebenzi ngamanye amaxesha babesetyenziswe ngokulandelelana ukuba basebenze kunye neontanga eziphezulu (okanye ezantsi). Ngethamsanqa, le venkile yayine-digital-age checkout system elandelelanisa izinto ngamnye umqeshi oye wazama ukuzenza ngawo onke amaxesha. Kusuka kule datha yokungena kwi-log, iMas kunye ne-Moretti bakwazi ukudala imilinganiselo ecacileyo, yodwa, kwaye isoloko isenza imveliso. Ukudibanisa ezi zinto zimbini-ukuhluka okwenzeka ngokwemvelo kwintsebenzo yontanga kunye nemilinganiselo yokuvelisa imveliso-iMas ne-Moretti inqikelele ukuba ukuba umqeshi wabelwe abasebenzisana nabo ababenemveliso engaphezulu kwe-10%, ukuveliswa kwayo kuya kwanda ngo-1.5% . Ukuqhubela phambili, basebenzise ubukhulu kunye nobuncwane beenkcukacha zabo ukuba bahlolisise imiba ebalulekileyo ebalulekileyo: i- heterogeneity yale mpawu (Ziziphi iindidi zabasebenzi umphumo okhudlwanayo) kunye neendlela ezisemva kwefuthe (Kutheni kubakho ukuveliswa kweentanga eziphezulu ezikhokelela ekubeni umkhiqizo ophezulu?). Siza kubuya kule micimbi ebalulekileyo-ukuchithwa kweempembelelo zonyango kunye neendlela-kwisahluko 4 xa sixoxa ngeemvavanyo ngokubanzi.

Ukuqulunqa kwezi zifundo zimbini, iitheyibhile 2.3 isishwankathela ezinye iifundo ezinesi sakhiwo esifanayo: kusetyenziswa umthombo wenkcazelo ehlala uhlala njalo ukulinganisa umphumo wezinye izinto ezingafaniyo. Ngokwenza oko, abaphandi basebenzisa iindlela ezibini ezahlukeneyo zokufumana iimvavanyo zendalo, zombini ziyakwazi ukuvelisa. Abanye abaphandi baqala nge-data-source rhoqo kwaye bajonga iziganeko ezingaqhelekanga kwihlabathi; abanye baqala umcimbi ongenakwenzeka kwihlabathi kwaye bafune imithombo yedatha ethatha impembelelo yayo.

Kwiingxoxo ngoku malunga nokuzama kwemvelo, ndishiye iphuzu elibalulekileyo: ukusukela kwimeko endikunike yona okokufunayo ngamanye amaxesha kuya kuba nzima. Masibuyele e-Vietnam umzekelo wolu hlobo. Kule meko, uAngrist unomdla ekuqikeleleni umphumo wenkonzo yempi kwimbuyekezo. Ngelishwa, inkonzo yezempi yayingekho i-random eyabelwe; kunoko kwakuqulunqwa ukuba kwakunikwe ngokulandelelana. Nangona kunjalo, akuyena wonke umntu owaqulunqwayo wakhonza (kukho iintlobo ezahlukeneyo zokuxolelwa), kwaye akusiyo wonke umntu owakhonzayo owabhalwa (abantu banokuzivolontiya ukukhonza). Kungenxa yokuba ukubhalwa kweso sibiwe ngokukhawuleza, umphandi unokulinganisa umphumo wokubhalwa kuwo wonke amadoda kwidrafti. Kodwa i-Angrist ayifuni ukwazi umphumo wokuqulunqwa; wayefuna ukwazi umphumo wokukhonza emkhosini. Ukwenza oku kuqikelelwa, nangona kunjalo, iimpembelelo ezongezelelweyo kunye neengxaki ziyafuneka. Okokuqala, abaphandi kufuneka bacinge ukuba indlela kuphela yokubhaliweyo eyimpembelelo yempembelelo yinkonzo yemikhosi, inkolelo ebizwa ngokuba ngumngcipheko wokukhutshwa . Le ngcamango ingalunganga ukuba, ngokomzekelo, amadoda aqoshiwe ahlala esikolweni ixesha elide ukuze aphephe ukukhonza okanye ukuba ngabaqeshi babengenakukwazi ukuqesha amadoda abhalwe. Ngokuqhelekileyo, ukuthintela ukukhutshwa kubaluleke kakhulu, kwaye kudla nzima ukuqinisekisa. Nangona ukuthintela ukukhutshwa okuchanekileyo, akunakwenzeka ukuqikelela umphumo wenkonzo kubo bonke abantu. Kunoko, kuba ngabaphandi banokuqikelela kuphela umphumo kwisigcawu esithile samadoda abizwa ngokuba ngabaxhamli (amadoda ayeza kukhonza xa aqulunqwe, kodwa akayi kukhonza xa engaqulunqwa) (Angrist, Imbens, and Rubin 1996) . Noko ke, abathengisi bekungenjalo ngabantu ababengumdla. Phawula ukuba ezi ngxaki zivela nakwiimeko ezicocekileyo ze-lottery. Isisombululo esongezelelweyo seengxaki zivela xa unyango lungafumaneki ngeloti yenyama. Ngokomzekelo, kwisifundo seMas no-Moretti sabantu abashicileli, kuphakanyiswa imibuzo eyongeziweyo malunga nokucingwa ukuba isabelo sabangontanga sisisigxina. Ukuba le ngcamango yachithwa ngamandla, ingaba neengcamango zabo. Ukugqiba, ukuhlolwa kwemvelo kungabakho isicwangciso esinamandla sokwenza uqikelelo lwangaphakathi kwimiba engeyiyo yokuhlola, kwaye imithombo yolwazi emikhulu inyuse amandla ethu okugxininisa kwizilingo zemvelo xa zenzeka. Nangona kunjalo, mhlawumbi kuya kufuna ukunyamekela-kwaye ngamanye amaxesha iingqiqo ezinamandla-ukuba zihambe ziphi uhlobo olunikezele ukuqikelela ukuba ufuna.

Isicwangciso sesibini endifuna ukukuxelela malunga nokwenza uqikelelo lwe-causal kwi-data engeyiyo yokuhlola kuxhomekeke kwi-statistically ukulungelelanisa idatha engeyiyo yokwenza umzamo wokwenza i-akhawunti ngenxa yokungafani kolu hlobo phakathi kwabo benzayo kwaye abazange bamkele unyango. Kukho iindlela ezininzi zokulungiswa, kodwa ndiya kugxila kumntu obizwa ngokufanayo . Ngokuhambelana, umphandi ukhangelelanisa idatha engeyiyo yokuzama ukudala iimbini zabantu abafana noko ngaphandle kokuba omnye ufumene unyango kwaye enye ayikho. Kwinkqubo yokufanisana, abaphandi ngokwenene baqhekeza ; oko kukuthi, ukulahla amatyala apho kungekho mdlalo ocacileyo. Ngaloo ndlela, le ndlela izakubizwa ngokuchanekileyo ngokuchanekileyo kunye ne-pruning, kodwa ndiya kubambelela kwikota yendabuko: ukufana.

Omnye umzekelo wegunya lezicwangciso ezihambelanayo kunye nemithombo yamandla engeyiyo yokuhlola evela kummandla wophando ngokuziphatha kwabaxhasi nguLiran Einav kunye noogxa (2015) . Babenomdla kwiintengiso ezenzeka eBay, kwaye ekuchazeni umsebenzi wabo, ndiza kugxininisa kwimpembelelo yentengo yokuqala kwintengiso kwiziphumo zentengiso, njengexabiso lokuthengiswa okanye ubunokwenzeka bokuthengiswa.

Indlela ehlukileyo kakhulu yokuqikelela umphumo wexabiso lokuqala kwixabiso lentengo kuba kukubala kuphela inani lokugqibela lezentengiso kunye namaxabiso okuqala ahlukileyo. Le ndlela yayiya kulungile ukuba ufuna ukuqikelela ixabiso lentengiso elinikwa intengo yokuqala. Kodwa ukuba umbuzo wakho uphathelene nomphumo wexabiso lokuqala, le ndlela ayiyi kusebenza ngenxa yokuba ayixhomekeke ekuthelekisweni okuthe tye; Iintengiso kunye namaxabiso okuqala aphantsi azinokuhluke kakhulu kulabo abanamaxabiso aphezulu okuqala (umz., banokuba ngeentlobo ezahlukeneyo zeempahla okanye badibanise iintlobo ezahlukeneyo zabathengisi).

Ukuba usuvele uyayazi iingxaki ezinokuvela xa wenza uqikelelo lwe-causal kwi-data engafumanekanga, ungasenqa indlela yokukhohlisa kwaye ucinge ngokusebenza kwintsimi yokuhlola apho ungathengisa khona into ethile-ithi, iqela legalufa-kunye isethi yee-parameters zetengiso-zithi, ukuthunyelwa kwamahhala kunye neentengiso kuvulwe iiveki ezimbini-kodwa ngamaxabiso okuqala angabelwe. Ngokuthelekisa iziphumo zemarike eziphumo, eli vavanyo lommandla luza kunika umlinganiselo ocacileyo wefuthe lexabiso lokuqala kwixabiso lentengo. Kodwa le milinganiselo iya kusebenza kuphela kwimveliso ethile kunye nokusetyelwa kweerameters. Iziphumo zinokuhluka, umzekelo, kwiintlobo ezahlukeneyo zemveliso. Ngaphandle kweengcamango eziqinileyo, kunzima ukuphucula phambili kulolu vavanyo olulodwa ukuya kuluhlu olupheleleyo lweemvavanyo ezingenzeka. Ukongezelela, iimvavanyo zentsimi zithengele ngokukhawuleza ukuba akunakukwazi ukuqhuba zonke iintlobo onokufuna ukuzizama.

Ngokuphambene neendlela ezingenangqondo kunye nokulinga, u-Einav kunye noogxa bathatha indlela yesithathu: ukufanisana. Iqhinga eliphambili kwisicwangciso sabo kukufumanisa izinto ezifana nokuhlola kwimihlaba esele yenzeka eBay. Ngokomzekelo, isibalo 2.8 sibonisa ezinye zezihlomelo ezingama-31 zeqela elifanayo legalufa-i-Taylormade Burner 09 Ukuthengiswa komqhubi-thengiswa ngumthengisi ofanayo- "i-budgetgolfer." Nangona kunjalo, ezi zihlomelo ezingama-31 zinempawu ezahlukileyo, ezifana nokuqala intlawulo, imihla yokuphela kunye nemirhumo yokuthumela. Ngamanye amazwi, kungathi "uhlahlo lwabiwo-mali" luqhuba iimvavanyo zabaphandi.

Ezi zihlomelo ze-Taylormade Burner 09 Umqhubi othengiswa yi-"budgetgolfer" ngumzekelo omnye wokudibanisa kwezihlomelo, apho kukho into efanayo into ekuthengiswa ngayo umthengisi omnye, kodwa ngezinye iimpawu ezahlukileyo. Kwiingxowa ezinkulu ze-eBay kukho ngokoqobo ngamakhulu amawaka eesethi ezidibeneyo ezibandakanya izigidi zezihlomelo. Ngaloo ndlela, kunokuba kuthelekise intengo yokugqibela kuyo yonke idilesi kunye nexabiso lokuqala lokuqala, u-Einav kunye noogxa baqhathaniswa kunye neeseti ezifanayo. Ukuze udibanise iziphumo ekuthelekisweni phakathi kwezikhulu zeenkulungwane zeetekethi, u-Einav kunye nabo basebenza nabo bavakalisa intengo yokuqala kunye nexabiso lokugqibela ngokwexabiso lokubaluleka kwento nganye (umzekelo, intengo yayo yentengiso yesilinganiso). Umzekelo, ukuba i-Taylormade Burner 09 Driver inexabiso lokubhengisa i-$ 100 (ngokusekelwe kwintengiso yayo), ngoko intengo yokuqala ye-$ 10 iya kuboniswa njenge-0.1 kunye nexabiso lokugqibela eli-$ 120 njenge-1.2.

Umzobo 2.8: Umzekelo wesethi ehambelana. Le yinto efana neyegalufa ye-golf (i-Taylormade Burner 09 Driver) ethengiswa ngumntu ofanayo ("ibhajethi"), kodwa ezinye zee ntengiso zenziwa phantsi kweemeko ezahlukeneyo (umzekelo, amaxabiso aqala okuqala). Yenzelwe imvume evela ku- Einav et al. (2015) , umfanekiso 1b.

Khumbula ukuba u-Einav kunye nabalingane bakhe banomdla kwimpembelelo yentengo yokuqala kwiziphumo zentengiso. Okokuqala, basebenzisa ukulungelelaniswa okusemgangathweni ukuba baqikelele ukuba amaxabiso okuqala aphezulu anciphisa amathuba okuthengisa, kwaye ukuba amanani aphezulu aqala ukunyusa intengo yokuthengisa yokugqibela (enemeko yentengiso eyenzekayo). Ngokwabo, ezi qi kelelo-ezichazela ulwalamano oluxubileyo kwaye zilinganiswe kuzo zonke iimveliso-akuzona zonke izinto ezithandekayo. Emva koko, u-Einav kunye noogxa basebenzise ubungakanani obukhulu beenkcukacha zabo ukudala iindidi ezininzi eziqingqiweyo. Ngokomzekelo, ngokuqikelela umphumo ngokwahlukileyo kwiintlobo ezahlukeneyo zokuqala, bafumanisa ukuba ubudlelwane obuphakathi kwentengo yokuqala kunye nentengo yentengiso akusiyo yonxibelelwano (umfanekiso 2.9). Ngokukodwa, ukuqala kwamaxabiso phakathi kwe-0.05 no-0.85, intengo yokuqala inefuthe elincinci kwixabiso lentengiso, ukufunyanwa okuye kwaphulwa ngokupheleleyo ngokuhlaziywa kwabo kokuqala. Ukuqhubela phambili, kunokuba kunomlinganiselo kuzo zonke izinto, u-Einav kunye nabalingane baqikelele ukuba impembelelo yentengo yeendidi ezingama-23 ezahlukeneyo zezinto (umzekelo, ukunikezwa kwezilwanyana, i-electronics, kunye neememorabilia zezemidlalo) (umfanekiso 2.10). Ezi ngqikelelo zibonisa ukuba izinto ezininzi ezahlukileyo-njengeememorabilia-intengo yokuqala inefuthe elincinane kumathuba okuthengiswa kunye nomphumo omkhulu kwixabiso lokuthengisa lokugqibela. Ukongezelela, ukufumana izinto ezininzi ezinokudityaniswa-njengeeDVD-intengo yokuqala ingaba nefuthe kwinqanaba lokugqibela. Ngamanye amazwi, umyinge odibanisa iziphumo ezivela kwiindidi ezahlukeneyo ezingama-23 zifihla ukungafani okubalulekileyo phakathi kwezi zinto.

Umzobo 2.9: Ulwalamano phakathi kwexabiso lexabiso lexabiso lezentengiso kunye neentengo zokuthengiswa (a) kunye nentengo yokuthengisa (b). Kukho ulwalamano olunxulumene phakathi kwentengo yokuqala kunye nokwenzeka okuthengiswayo, kodwa ulwalamano olungelona luhlobo phakathi kokuqala kwentengo kunye nentengo yentengiso; ukuqala kwamanani phakathi kuka-0.05 no-0.85, intengo yokuqala iyaba nefuthe elincinci kwixabiso lentengiso. Kuzo zombini iimeko, ubudlelwane buhlala buzimeleyo kwintengo yento. Ukutshintshwa kwi- Einav et al. (2015) , amanani 4a no-4b.

Umzobo 2.10: Uqikelelo lweqela ngalinye lezinto; icandelo eliqinileyo liqikelelwa kuzo zonke iindidi ezihlanganiswe ndawonye (Einav et al. 2015) . Ezi ziqikelelo zibonisa ukuba izinto ezininzi ezahlukileyo-njengeememorabilia-intengo yokuqala kuyenomphumo omncinci kwintengiso ( \(x\) -axis) kunye nomphumo omkhulu kwixabiso lokuthengisa lokugqibela ( \(y\) -axis). Ukutshintshwa kwi- Einav et al. (2015) , umfanekiso 8.

Nangona ungekho umnqweno omkhulu kwiintengiso kwi-eBay, kufuneka ubabaze indlela eya ku-2.9 kunye nombolo 2.10 unikezela ukuqonda okucebileyo kwe-eBay kunokuqikelela okulula ukuchaza ubudlelwane obudibeneyo kunye nokudibanisa iindidi ezininzi zezinto. Ukongezelela, nangona kungenokwenzeka ukuba izazinzululwazi zikwazi ukuvelisa ukuqikelela okucaceleyo kwimizamo yenkalo, iindleko zenza loo mvavanyo ingenakwenzeka.

Njengazo zilingo zendalo, kukho iindlela ezininzi ezihambelana nokukhokelela. Ndicinga ukuba inkxalabo enkulu kwiingqikelelo ezihambelanayo kukuba banokubakhokelwa yizinto ezingasetyenziswanga ukuhambelana. Ngokomzekelo, kwiziphumo zabo eziphambili, u-Einav kunye nabo basebenzisana nabo bafana ngokufanayo kwizinto ezine: inombolo yesazisi yomthengisi, umxholo wento, isihloko somxholo, kunye nomxholo ongaphantsi. Ukuba izinto zahluke ngeendlela ezingasetyenziselwa ukufanisana, oko kungenza ukuthelekiswa okungafanelekanga. Umzekelo, ukuba "i-budgetgolfer" iyancishisa amanani kwi-Taylormade Burner 09 Umqhubi ebusika (xa iiklabhu zegalufu zingabonakali kakhulu), ngoko kuya kubonakala ukuba amaxabiso okuqala aphantsi akhokelela kumaxabiso athile okugqibela, xa okunene oku kuya kuba yinto ukuhluka kwexesha ngexesha lokufuna. Enye indlela yokujongana nale nkxalabo izama ezininzi iintlobo ezahlukeneyo ezihambelanayo. Ngokomzekelo, u-Einav kunye nabalingane baphinda bahlalutya uhlalutyo lwabo ngelixa behlula iifestile kweso esetyenziselwa ukufanisana (iiseti ezifanisiweyo zibandakanya izinto ezithengiswayo kunyaka owodwa, kwinyanga enye, kunye nokukhathazeka). Ngenhlanhla, bafumanisa iziphumo ezifanayo kwiifestile zonke zexesha. Olunye uxhala kunye nokuchasana luvela kwiinguqulelo. Uqikelelo oluchanekileyo luhambelana nolwazi oluchanekileyo; azisebenzi kwiimeko ezingenakufaniswa. Ngokomzekelo, ngokunciphisa uphando lwabo kwizinto ezinokuluhlu olubanzi, u-Einav kunye noogxa bajolise kubathengisi abaqeqeshiweyo nabaqeqeshiweyo. Ngaloo ndlela, xa ukutolika ezi ngqamaniso kufuneka sikhumbule ukuba zisebenza kuphela kule ngqutyana ye-eBay.

Ukuqhagamshelana isicwangciso esinamandla sokufumana ukuthelekiswa okuthe tye kwiinkcukacha ezingezizo. Kwiintlobo ezininzi zenzulululwazi zentlalo, ukufana kufakalelwa okwesibini ukulungela ukuzama, kodwa leyo yinkolelo enokuthi ihlaziyeke, impela. Ukudibanisa kwedatha enkulu kunokuba ngcono kunenani elincinci lokuhlola kwimihlaba xa (1) i-heterogeneity kwimiphumo ibalulekile kwaye (2) iinguqu ezibalulekileyo ezifunekayo zokufanisana ziye zalinganiswa. Itheyibhile 2.4 inikeza ezinye iimzekelo zendlela ukufanisana kungasetyenziselwa ngayo imithombo ebanzi yedatha.

Ekugqibeleni, ukuqikelela iziphumo ze-causal kwi-data engekho yoluvavanyo kunzima, kodwa iindlela ezifana nokuhlolwa kwemvelo kunye nokulungiswa kwamanani (umz. Ukulinganisa) kunokusetyenziswa. Kwezinye iimeko, ezi ndlela ziyakwazi ukungahambi kakuhle, kodwa xa zisetyenziswe ngokucophelela, ezi ndlela zingabancedisa indlela yokuhlola endiyichazayo kwisahluko 4. Ngokuqhubekayo, ezi ndlela zimbini zibonakala zinokuzuza ngokukhula kwimihla ngemihla- kwiinkqubo ezinkulu zeenkcukacha.