Welcometotheworkbook!

• Thisworkbookisintendedtobereadalongwiththevideo.I’vetriedtoincludeanythingnotincludedinthevideo.You’llalsofindexercisesnotincludedinthevideos.Takeyourtimetodothembeforewemoveon.Forthislesson,youalsoneedyourJune2007PrepTestonhand.Let’sgetstarted!

Yourfirstpreptest

• Don’tworrytoomuchaboutyourscore.It’sjustabaselinetoseehowmuchyouneedtoimprovetogetthescoreyouwant.Asyoucanseeinthevideo,evenslightimprovementsinyourrawscore(thenumberofquestionsyougetright)canleadtodramaticimprovementsinyourpercentile(thepercentageofstudentsthathavealowerscorethanyou).

LessonTwo:LogicalReasoning

• Solet’sgetstartedwithLogicalReasoning.Here’saquestionfromyourrecenttest:

• June2007,SectionII,#21• Ithinkthatyoushouldreadthepassage,notthequestion,first.Ifeelthatonebecomesabetterreaderandanalyzerofargumentsthisway.Othersmightdisagree,andultimately,it’suptoyoutodecidewhatmethodisbestforyou.

June2007,SectionII,#21• Thefirststepistounderstandthatthisisapoorargument.Evenifweareconvincedbythereasoning,thequestionsasksusforwheretheargumentis“mostvulnerabletocriticism”implyingthattheLSATthinksthisisabadargument.

• Itisanoversimplificationtosaythat“theLSATthinks.”TheLSATquestionsarewrittenbythousandsofindividualauthors.Butasweshallsee,thesethousandsofauthorsproducequestionsthatall“think”roughlythesameway.Ifwecanlearnmoreaboutthiskindofthinking,we’llbewellonourwaytomasteringthetest.

June2007,SectionII,#21

• SotheLSATthinksthisargumentisabadone?Why?Becausetheevidencedoesnotfullysupporttheconclusion.OntheLSAT,wealmostnevergettotherightanswerbydoubtingtheevidence.ItmightbetruethattheDriverhasdonesomepoorresearchandthataccidentratesarereallynotlowerforminivans,butontheLSAT,weaccepttheevidence,yetdoubttheconclusion.Soweacceptthatminivanshaveloweraccidentratesthansportscars,butwedoubtthatchangingcarswouldcausetheDrivertodrivemoresafely.

June2007,SectionII,#21

• Itisaprettysillyconclusion,soit’snothardtoseethatitisflawedinsomemajorway.Mostofusrealizethatit’snotthekindofcar,butthedriver,whoisresponsiblefordrivingsafelyorrecklessly.ButthedifficultpartoftheLSATistranslatingourgutresponsethattheargumentispoorintoacorrectanswer.

June2007,SectionII,#21

• Soweareaskedtochooseananswerthattellsuswheretheargumentisatitsmostvulnerable.Sowehavetoaskourselves,whatdidthisargumentdo?Itgaveevidencethatminivanshaveloweraccidentratesthansportscars.Itconcludedthataminivanwouldcausethedrivertodrivemoresafely.Clearly,then,thereissomekindofcauseandeffecterrorhere.

June2007,SectionII,#21• Inthedriversmind,hisresearchfindings,thatminivanshavealoweraccidentrate,provedthatowningaminivanwouldcausehimtodrivemoresafely.Thedrivertookevidenceofacorrelation(whichisjustafancywordforsomekindofstatisticalrelationship)andmistakenlyconcludedthattherelationshipwascausal.What’sreallygoingonhereisthatminivanshaveloweraccidentratesthansportscarsbecausedifferentkindsofdriversbuydifferentkindsofcars.Ifoursamerecklessdriverpurchasedaminivan,heprobablywouldbejustaslikelytocrashitashewouldacorvette.Let’stakealookattheanswerchoices:

June2007,SectionII,#21

• A)"infersacausefromamerecorrelation": correlationsareverycommonontheLSAT,soyoumustunderstandhowtheycanbeemployedcorrectlyandincorrectlyinordertogetalargenumberofquestionsright.Acorrelationisastatisticalrelationshipthatappearsnottobemerelycoincidental. Therearepositivecorrelations:asyourLSATscoreincreases,yourchancesofgettingintoYaleincrease.

June2007,SectionII,#21

• Therearealsonegativecorrelations:themoreoneexercises,thelesslikelyitisthatonewillhaveheartdisease. Inthelasttwoexamples,itisclearthattherealsoacausalrelationshipatwork.WeknowthatahighLSATscoreisamajorfactor(afactorisasynonymforacause)ingettingintoagoodlawschool,justasweknowthatexerciseisafactorinhavingahealthyheart.

June2007,SectionII,#21

• Buttherecanbeothercorrelationsthatdonotnecessarilyimplyacausalrelationship. Let'ssaythatwedidastudythatshowedthatvegetariansweremorelikelytolivelongerthanmeat-eaters.Suchastudysuggeststhatbeingavegetariancontributestolongevity,butit isalsopossiblethatvegetariansmightengageinotherhealthybehaviors(exercise,notsmoking,etc)thatarethetruecauseoftheirlongerlifespans.

June2007,SectionII,#21

• “A”statesclearlywhattheargumentdidincorrectly.Ontestday,ifwehavedonetheworkanalyzingtheargumentproperly,wecouldconfidentlypickAandmoveon.Butfornowit’sinstructivetolookattheincorrectanswers.Also,eventhebestLSATtest-takerswillsometimesnotseeexactlywhatanargumentdidimproperly,andsowillhavetodecidebetweenthecompetinganswerchoices.

June2007,SectionII,#21

• B)“reliesonasamplethatistoonarrow.”Thismightbetrue.Wereallyknownothingabouthowextensivethedriver’sresearchwas.Butbecauseweknownothingaboutthedriver’sresearch– itssources,thesizeofitssample–wewanttoavoidthisanswerchoice.It’sspeculative,whereaswehaveclearproofthatthedriverdefinitelycommittedtheerrorinanswerchoiceA.

June2007,SectionII,#21

• C)“misinterpretsevidencethataresultislikelyasevidencethataresultiscertain.”CwouldbebetteriftheargumenthadevidencethatminivansDOcauseamajorityofdriverstodrivemoresafely,andthenthedriverconcludedthat,afterpurchasingaminivan,hedefinitelyWILLbeasaferdriver.ButCfailsbecausetheargument’sevidencedoesn’tevendothat.Itonlyestablishesacorrelation,andit’stheleapfromcorrelationtocausationthatistheargument’sfatalflaw.

June2007,SectionII,#21

• D)"mistakesaconditionsufficientforbringingaboutaresultforaconditionnecessaryfordoingso“.Sufficient/necessaryreversalsareextremelycommonontheLSAT,soyouneedtobeawareofthem.Inthisargument,however,therearenoneofthekeywordsthatindicateconditionalreasoning.Suchwords(all,every,if, when,only,depends,unless,except,etc.)mustbepresentinordertodeclarethatanswerchoicelikeDiscorrect. (Forafurtherdiscussionofsufficientandnecessaryconditions,seetheanalysisof23.)

June2007,SectionII,#21

• E)"reliesonasourcethatisprobablynotwell-informed": WehavenoindicationthattheDriver'ssourcesaresuspect.Therefore,itwouldbeamistaketospeculateastowhetherornothissourcesareappropriate. Actually,attackingthesourcesforanargument'sevidenceisusuallyamajorLSATflaw.

• Let’slookatanotherproblemthatcontainsabadargument:

June2007,SectionII,#17• Thefirststepisanalyzinganyargumentisidentifyingtheconclusion.The

conclusionisthat,"weshouldmaketheprotectionofourclient'sconfidentialityourhighestpriority."Usually,conclusionscanbeidentifiedthroughconclusionkeywords.We’lldiscussthesekeywordsfurtherwhenwegetintoMainPointsquestionsinLesson4.Althoughtherearenotypicalconclusionkeywordshere, therearetwofeatures ofthelastsentence thatindicateitcontainstheargument'smainpoint:

1)"Inlightofthistestimony":thisphraseintroducesthatlastsentence,andtellsusthatthetestimonysupportswhatfollows.

2)"weshouldmake":conclusionsoftentelluswhattheauthorthinkswe"should"do. Theargumentstartswiththeopinionof"computerexperts"whichformsthebasisofacalltoaction,whatwe"should"do.

June2007,SectionII,#17• Wordslike "should"and"ought"donotdescribetheworldasitis;

theyindicatetousagoodcourseofaction.Statementsthatcontainwordssuchasthesearecalled"prescriptive"becausethey(likeadoctor)"prescribe"whatweoughttodo.Youmightalsomighthearthemreferred toas"normative,"becausesuchstatementsalsocanbeusedtodefinewhatisproper,"normal"behavior.("Youshouldbrushyourteethtwiceaday.")Statementsthatmerelydescribetheworldarecalled,simplyenough,"descriptive.“We’lltalkmoreaboutthisprescriptive/descriptive distinctionwhenwecoverAssumptionsinLesson9andPrincipleQuestionsinLesson13.Fornow,it’senoughtoknowthatprescriptivestatementsareoftenpartofaconclusion,becauseaconclusionistryingtoconvinceusofwhatwe“should”believeordo.

June2007,SectionII,#17

• Weknowwhattheconclusionis,andweknowit’sabadone,becausethequestionstemtellsustofindthe“objection”towhichtheargumentis“mostvulnerable.”Sowhatiswronghere?Theevidenceisthat“severalcomputerexpertsmaintainedthatthemostsignificantthreatfacedbylargeinstitutionssuchasuniversitiesandhospitalsisunauthorizedaccesstoconfidentialdata.”Sowhyiswrongforahospitalexecutivetoconcludethat“weshouldmaketheprotectionofourclients’confidentialityourhighestpriority”?

June2007,SectionII,#17

• Well,let’sthinkaboutthisisthesimplesttermspossible:whatdoyouthinkshouldbeahospital’shighestpriority?Idon’tknowaboutyou,butwhenIgotoahospital,I’mmostconcernedwithleavingalive,andamoreminorconcernmightbemyprivateinformationbeinghackedbyWikileaksorNewsCorporation.Also,it’soddthatthehospitalexecutivewouldonlyseektheopinionofacomputerexpert.Wouldn’titalsobeworthwhiletoconsulttheopinionsofdoctors,nurses,patients,and,heavenforbid,maybeevenlawyers?

June2007,SectionII,#17• Let’slookattheanswerchoices:• A)“Theargumentconfusesthecausesofaproblemwiththeappropriatesolutionstoaproblem.”Thischoicedoesn’tseemtoapplyatall.The“causes”ofunauthorizedaccessarenotdiscussed.Thiskindofchoicemightbetemptingforsomestudents,becausetheydon’tgetit,andfeelthattheLSATistryingtoplayatrickonthem.Usually,ifyoudon’tunderstandachoice,yetyouunderstandallthewordsinthechoice,thechoiceismeaninglessinthecontextoftheargumentandthereforeincorrect.Don’tevenletyourselfgetbulliedbyachoice:ifyoudon’tgetit,it’sprobablynotyouthat’swrong,butthechoiceitself.

June2007,SectionII,#17

• B)“Theargumentreliesonthetestimonyofexpertswhoseexpertiseisnotshowntobesufficientlybroadtosupporttheirgeneralclaim.”Thisisthecorrectanswerchoice,andallit’sreallysayingisthatthesecomputerexperts(unlessweweretoldthattheyarealsodoctors,ornurses,orpatients,orlawyers),don’thavetheknowledgetodecidewhatshouldbethehighestpriorityforahospital.

June2007,SectionII,#17

• C)“Theargumentassumesthatacorrelationbetweentwophenomenaisevidencethatoneisthecauseoftheother.”Thisisthesameflawfromthepreviousquestion,itwascorrectthen,butit’swronghere.IhopeyoucanseehowlearningthecommonLSATflawscanreallyhelpyourperformanceonLogicalReasoning.We’lldiscussthisfurtherinLesson8.

June2007,SectionII,#17• D)“Theargumentdrawsageneralconclusionabouta

groupbasedondataaboutanunrepresentativesampleofthatgroup.”ThischoiceissimilartoBfromthepreviousquestion,theanswerchoicethatsaidthattheDriver’sresearchwasbasedontoonarrowasample.WhilethiscanbetheflawonaLogicalReasoningquestion,thereisusuallyspecificevidencethatthesampleistoosmallordrawnfromapartofagroupthatprobablydoesnotspeakforthewhole.Perhapsthesecomputerexpertsareparticularlycrazy.ButevenifALLcomputerexpertseverywhereagreedthatprotectingconfidentialityshouldbethehighestpriority,theirexpertisewouldnotbewideenoughtodictatewhatalarge,complexinstitutionlikeahospitalshoulddo.

June2007,SectionII,#17

• E)“Theargumentinfersthatapropertybelongingtolargeinstitutionsbelongstoallinstitutions.”Theargumentnevermakesaleapfromlargeinstitutionstoallinstitutions,sothischoiceisclearlyincorrect.

June2007,SectionII,#17• YoumayhavenoticedthatIreliedabitoncommonsenseearlier.ThoseofyouwhohavetakenanotherLSATcoursemightobject:“MyteachertoldmethatcommonsenseplaysnorollontheLSAT,thattherealworlddoesn’tmatter,thatonlythepassageisreal.”Well,that’sjustnottrue.Ifweweren’tabletouseourcommonsenserealizationthatahospitalhasmoreimportantthingstoworryaboutthanhidingapatient’sprivateinformation,wewouldprobablyfindthatquestionmuchmoredifficult.Youdon’thavetotakemywordforit.Let’sseewhattheLSATauthorshavetosay:

LogicalReasoningInstructions

LogicalReasoningInstructions

• Thepassagetrumpsanyoutsideknowledge.ButyoucanusecommonsenseontheLSAT,let’sjustmakesurethatitisgoodcommonsense.PartoflearningtheLSATislearninghowtorefineyourthinkingsoyourownintuitivereasoningbecomesmorepreciseandmorepowerful.Nowlet’stackleanotherquestion.

June2007,SecIII,#25• Theconclusionisintroducedbyconclusionkeyword,“hence.”We’llsaymoreaboutconclusionkeywordswhenwediscussMainPointquestionsinLesson4.Theconclusionis“theanthropologists’claimisfalse.”Sowhatwasthatthatclaim?Theargumentbeginswiththatclaim,“Someanthropologistsargue….”.Thisargumentstructureisverycommon:theargumentbeginswithaclaimaboutwhat“somepeoplethink,”concludesthatthisclaimisfalse.Soreally,theconclusionisthat“thehumanspeciescouldnothavesurvivedprehistorictimesifthespecieshadnotevolvedtheabilitytocopewithdiversenaturalenvironments”isfalse.Whatistheevidenceforthis?

June2007,SecIII,#25

• Theevidenceisofonespecies,AustralopithecusAfarensis,whichhadhadsuchanabilitytocopewithdiverseenvironments,butdidnotsurvive.Sowhyisthisevidencenotenoughtoprovetheconclusionistrue?BecauseitisstillpossiblethathumansNEEDEDtheabilitytosurviveindiverseenvironments,evenifsuchanabilityisnotenoughtoguaranteesurvival.Let’snowtakealookattheanswerchoices.

June2007,SecIII,#25

• A)Thisisthecorrectanswer.Thelanguagemightbeconfusing,butallitissayingisthattheargumentconfusesaconditionthatisrequired(“necessary”),i.e.,theabilitytocopewithdiverseenvironments,withonethatisenoughtoensuresurvival(“sufficient”).Theanthropologistsclaimedthatsuchanabilitywasnecessary.Theargumentclaimedthatsuchanabilitywasnotsufficient,becauseAustralopithecusAfarensisbecameextinct,andsotheanthropologistswerewrong.Let’sthinkofasimilarlyflawedargument:

June2007,SecIII,#25• David:Waterisnecessaryforsurvival.• Sean:Noit’snot.MyuncleShamushadplentyofwater,

andhestilldied.• It’sclearherethatDavidwasnotsayingthatwateris

sufficient,thatitguaranteessurvival.Hisclaimwasthatitwasnecessary.Sean’sargumentfailsbecauseingivinganexamplethatprovesthatwaterisnotsufficient,hehasdonenothingtodisproveDavid.Thisargumentisanalogoustothatin#25,becausethearguerdidnothingtodisprovetheanthropologists’claim.Theargueronlyshowedthatanabilitytocopewithdiverseenvironmentsisnotsufficient,soitisincorrecttosaythattheanthropologistsare“wrong”

June2007,SecIII,#25

• Thisquestionintroducedthethemeofsufficientandnecessaryconditions,whichistheoneofmostimportantanddifficulttopicsinLSATprep.Butbeforewediscussthistopicfurther,let’stakeaquicklookattheotheranswerchoices.

June2007,SecIII,#25

• B)Thischoicementionsa“relatedextinctspecies”butthereisnospecificspeciesmentionedotherthanAustalopithecusafarensis.Sothischoicemustbeincorrect.

• C)Thischoicementionsaspeciesthatsurvived,butallthatismentionedintheargumentisaspeciesthatwentextinct.Sothisisclearlyincorrect.

• D)Thischoiceiskindofinteresting,becauseclearlythearguer“failedtoconsider”lotsoffactorsthatmighthaveledtoAustalopithecusafarensis’ extinction.Soit’stempting.Butwhenchoosingtheargument’smostvulnerableweakness,weshouldfirstfocusonwhattheargumentactuallydid,ratherthanwhatitfailedtodo.Themostseriouserroristheconfusionofsufficientandnecessaryconditions,soAremainsabetterchoice.

June2007,SecIII,#25

• E)describesacauseandeffecterror.Butthisargumentdoesn’tdealwithcauseandeffect.ItnevertellsuswhyA.A.wentextinct.Sothischoicedoesn’tapplytothisargumentandisthereforeincorrect.

ConditionalReasoning

• Nowlet’sdiscussmoredeeplyoneofthemostvexingtopicsforLSATstudents,conditionalreasoning,whichinvolvesthediagrammingofsufficientandnecessaryconditions.