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TH EUNIVERSIT

YO FNORT HCAROLIN

A AT CHAPELHILL 

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Th eL.L . Thurston ePsychometri cLaboratory Th eUniversityo f NorthCarolin aa

tChape lHill Davi eHall01 3 A ChapelHill , N.C . 2751 4 Septembe r 25 , 1984

MEMORANDU M TO : Joh n Haines , Chie f Ambien t Standard s Branch , Sectio n B FROM : Thoma s S . Wallste n 

# T&i/ RE : Developmen t o f hemoglobi n protoco l an d selectio no f consultant s Th e purpos e o f thi s memorandumi s t o describ e th e proces s by whic hw e hav e develope d th e protoco l fo r encodin g probabilisti c judgment s abou t dose—respons e function s fo r hemoglobi ndecrement , and t o indicat e whic hexpert s w e hav e consulted . OAQP S specifie d th e advers e healt heffect s fo r whic h probabilisti c judgment s abou t dose-respons e function s wer e required , includin g hemoglobi n decrement . Afte r becomin g generall yfamilia r wit hth e Draf t Criteri a Documen t (CD ) wit hBo b Kallam' s and Jef f Cohen' s help , w e the nrea d mor e carefull yth e relevan t portion s o f th e C D and discusse d the ma t lengt hwit h suitabl e experts , wh o i nfac t fo r th e mos t par t wer e th e author s o f thos e portions . W e the n prepare d a firs t draf t o f th e protoco l section s 2-6 , whic hstructure d th e problem , and wen t bac k wit hi t t o thes e expert s a s wel l a s t o others . Th e additiona l expert s wer e draw n fro mth e populatio no f peopl e whos e judgment s migh t b e encoded , and wheneve r possibl e include d member s o f th e Ris k Assessmen t Subcommittee . W e worke d wit h thes e experts , structurin g th e proble mi nth e manne r w e woul d i f w e wer e goin g t o encod e thei r judgments , and revisin g th e protoco l accordingly . I nthi s fashion , th e protoco l wen t throug h a numbe r o f drafts . Whereve r i t wa s clea r tha t al l th e respondent s viewe d th e proble mi n th e sam e way , thi s wa ywa s specifie d i nth e protocol . Whereve r the ydiffered , o r indicate d tha t other s migh t diffe r fro mthem , w e provide d freedo mt o individualiz e th e scenari o fo r th e specifi c expert , subjec t onl y t o th e constraint s tha t th e obtaine d judgment s coul d ma p int o tr-.- . res t o f th e model , and b e comparabl e acros s experts . W e worke d primarilybwit hfiv e expert s i ndevelopin g t h protocol : Drs . Anit a Curran , Julia nChisolm , Leste r Grant , bP. 3

Memorandu m Mr . Joh n Haine s Septembe r 25 , 198 4 pag e 2 Hammond , and Pau l Mushak . Th e protoco l i s structure d i na wa y the yconside r reasonabl e and i nwhic hthe ywoul d fee l comfortabl e providin g th e desire d probabilisti c judgments. . Sectio n1 o f th e protoco l i s a nintroduction , indicatin g wha t w e ar e attemptin g t o d o and whyw e ar e doin g it . Section s 2 throug h5 precisel yspecif yal l th e parameter s o f th e problem , s o tha t th e dose-respons e function s ar e wel l defined . Sectio n6 , entitle d "Factor s t o Consider, " i s particularl y important . Th e poin t o f thi s sectio ni s t o elici t discussio n fro mth e exper t o nrelevan t theorie s and data . Thi s wil l hel p u s t o insur e tha t w e hav e th e proble mstructure d properl yfo r hi mo r her , caus e th e exper t t o consciousl yrevie whi s o r he r knowledg e prio r t o providin g probabilit yjudgments , and provid e a basi s fo r understandin g discrepan t judgments , shoul d the yoccur . Sectio n8 i s designe d t o elici t th e expert' s opinio nabou t possibl e advers e healt heffect s associate d wit helevate d erythrocyt e protoporphyri n levels . Materia l i nthi s sectio nwil l b e discusse d followin g th e forma l probabilit yencoding . Section s 7 and 9 relat e t o th e probabilit yencoding , and deriv e fro mou r prio r wor k o nencodin g probabilit yjudgment s abou t dose-respons e function s (Wallsten , Forsyth , and Budescu , 1983) . Sectio n7 provide s suggestion s o nho wt o minimiz e variou s possibl e biase s i n probabilit yencoding , and Sectio n9 i s a rathe r detaile d discussio n o f th e actua l probabilit yencodin g procedure . I t i s no t ou r intentio ntha t th e protoco l simpl yb e rea d by th e expert , followin g whic hprobabilit yjudgment s ar e collected . Rather , th e protoco l i s t o b e use d byth e analys t t o guid e discussio nand interactio n wit hth e expert . Section s 1 throug h8 o f th e protoco l wil l hav e bee n sen t t o th e exper t ahea d o f tim e fo r review . Then , bot hpartie s wil l hav e th e protoco l i nfron t o f them , and wil l activel ywor k together , usin g i t a s a focus . cc : J . Cohe n T . Feagan s R . Whitfiel d