统计学的成功案例和警示故事.ppt

StatisticsSuccessStoriesandCautionaryTales统计学的成功案例和警示故事 LESSON1第一课 1 1WHATISSTATISTICS 什么是统计学 Statisticsisacollectionofproceduresandprincipleforgatheringdataandanalyzinginformationinordertohelppeoplemakedecisionswhenfacedwithuncertainty 统计学是一套收集数据和分析信息的方法和原则 以帮助人们在面对不确定性时制定决策 Theoddsoffindingtwoidenticalfingerprintswere1in64billion FrancisGalton 两个随机个体具有相同DNA图形的概率为3 10 11 如果同时用两种探针进行比较 两个个体完全相同的概率小于5 10 19 每支枪的枪管都有独一无二的特征 这种特征影响了它所发射的每一发子弹 司法弹道学 航空公司通过抽样而省钱 最早的英文原版 打败庄家 1 2SEVENSTATISTICALSTORIESWITHMORALS7个包含寓义的统计学故事 Therearethreekindsoflies lies damnedliesandstatistics BenjaminDisraeli BritishPrimeMinister 1804 1881 CASESTUDY1 WhoareThoseSpeedyDrivers 谁是快车手 Responsesto What sthefastestyou veeverdriven Dotplot Responsesto What sthefastestyou veeverdriven Five numbersummary 一条平均水深0 4m河流绝不会比一个平均水深0 6m的游泳池更安全 Responsesto What sthefastestyou veeverdriven Five numbersummary Definition Themedianisthevalueinthemiddlewhenthenumbersareputinorder Thelowerquartileandupperquartileare roughly themediansofthelowerandupperhalvesofthedata Moralofthestory Simplesummariesofdatacantellaninterestingstoryandareeasiertodigestthanlonglists CASESTUDY2 DisasterintheSkies 空中的灾难 Planesgetcloserinmidairastrafficcontrolerrorsrise Errorsbyairtrafficcontrollersclimbedfrom746infiscal1997to878infiscal1998 an18 increase USATODAY Levin 1999 Theerrorspermillionflightshandledbycontrollersclimbedfrom4 8to5 5 5 5 4 8 114 6 Definition Therateissimplythenumberoftimessomethingoccurspernumberofopportunitiesforittooccur Baselinerateistherateatabeginningtimeperiodorunderspecificconditions Moralofthestory Whendiscussingthechangeintherateorriskofoccurrenceofsomething makesureyoualsoincludethebaserateorbaselinerisk CASESTUDY3 Didanyoneaskyouwhomyou vebeendating AccordingtoanewUSAToday GallupPollofteenagersacrossthecountry 57percentofteenswhogooutondatessaythey vebeenoutwithsomeoneofanotherraceorethnicgroup USATODAY Perterson 1997 CASESTUDY3 Inmostcases parentsaren tamajorobstacle Sixty fourpercentofteenssaystheirparentsdon tmindthattheydateinterracially orwouldn tmindiftheydid SacramentoBee Hiram 1997 Howcouldthepolltakersmanagetoasksomanyteenagersthesequestion Question1 CouldsuchasmallsamplepossiblytellusanythingaboutthemillionsofteenagersintheUnitedStates Question2 Yes ifthoseteensconstitutedarandomsamplefromthepopulationofinterest Howaccuratecouldthissamplepossiblybe Question3 Theresultsofthispollareaccuratetowithinamarginoferrorofabout4 5 95 confidenceinterval Moralofthestory Arepresentativesampleofonlyafewthousand orperhapsevenafewhundred cangivereasonablyaccurateinformationaboutapopulationofmanymillions CASESTUDY4 WhoAreThoseAngryWomen Awell conductedsurveycanbeveryinformative butapoorlyconductedonecanbeacompletedisaster Statistics ConceptsandControversives DavidS Moore Thewomenwhorespondedwerefedupwithmenandeagertofightthem Forexample 91 ofthosewhoweredivorcedsaidtheyhadinitiatedthedivorce Theangerofwomentowardmenbecamethethemeofthebook WomenandLove Shere Hite ShereHitesentquestionnairesto100 000womenaskingaboutlove sex andrelationships TheHitesampleexemplifiesoneofthemostcommonproblemswithsurveys thesampledatamaynotrepresentthepopulation Extensivenonresponsefromarandomsample ortheuseofaself selected i e all volunteer sample willprobablyproducebiasedresults Moralofthestory Anunrepresentativesample evenalargeone tellyoualmostnothingaboutthepopulation Definition Nonresponsebiascanoccurwhenmanypeoplewhoareselectedforthesampleeitherdonotrespondatallordonotrespondtosomeofthekeysurveyquestions Thismayoccurevenwhenanappropriaterandomsampleisselectedandcontacted Magazines televisionstations andinternetwebsitesroutinelyconductthesurveywhichisbasedonanonrepresentativesample usuallythosewhofeelstronglyabouttheissues Thesampleiscalledaself selectedsampleoravolunteersamplewhichtellsnothingaboutthelargerpopulationatall itonlytellsyouaboutthosewhoresponded CASESTUDY5 DoesPrayerLowerBloodpressure PrayerCanLowerBloodPressure AttendingreligiousserviceslowersbloodpressuremorethantuningintoreligiousTVorradio anewstudysays USATODAY Davis 1998 Peoplewhoattendedareligiousserviceonceaweekandprayedorstudiedthebibleonceadaywere40 lesslikelytohavehighbloodpressurethanthosewhodon tgotochurcheveryweekandprayedandstudiedthebibleless AnobservationalstudyconductedbytheU S NationalInstitutesofHealth whichfollowed2391peopleaged65orolderforsixyears Background Criticism Moralofthestory Cause and effectconclusionscannotgenerallybemadebasedonanobservationalstudy Definition Anobservationalstudyisoneinwhichparticipantsaremerelyobservedandmeasured Aconfoundingvariableisavariablethatisnotthemainconcernofthestudy butmaybepartiallyresponsiblefortheobservedresults CASESTUDY6 DoesAspirinReduceHeartAttackRates Background Time 1983 1988Organizer SteeringCommitteeofthePhysicians HealthStudyResearchGroupObjective Todetermineiftakingaspirinreducestheriskofaheartattack Subject 22 071malephysiciansbetweentheagesof40and80Method Afive yearrandomizedexperiment Method 2x2factorialdesign activeaspirinandactivebeta carotene 5 517 activeaspirinandbeta caroteneplacebo 5 520 aspirinplaceboandactivebeta carotene 5 519 aspirinplaceboandbeta caroteneplacebo 5 515 Aspirinreducedtheriskoffirstmyocardialinfarctionby44 Plessthan0 00001 Thereweretoofewstrokesordeathsuponwhichtobasesoundclinicaljudgmentregardingaspirinandstrokeormortality Result NewEnglandJournalofMedicine 1989 321 3 18 185 TheEffectofAspirinonHeartAttacks Morethan170otherfindingshaveemergedfromthetrialsofar Moralofthestory Unlikewithobservationalstudies cause andeffectconclusionscangenerallybemadeonthebasisofrandomizedexperiments Definition Arandomizedexperimentisastudyinwhichtreatmentsarerandomlyassignedtoparticipants Astatisticallysignificantrelationshipofdifferenceisonethatlargeenoughtobeunlikelytohaveoccurredinthesampleiftherewasnorelationshipordifferenceinthepopulation CASESTUDY7 DoestheinternetIncreaseLonelinessandDepression greateruseoftheinternetwasassociatedwithdeclinesinparticipants communicationwithfamilymembersinthehousehold declinesinsizeoftheirsocialcircle andincreasesintheirdepressionandloneliness Internetparadox Asocialtechnologythatreducessocialinvolvementandpsychologicalwell being AmericanPsychologist 1998 53 9 1017 1031DavidS Moore Sad LonelyWorldDiscoveredinCyberspace AmyHarmon August30 1998 Sunday Background Thestudyincluded169individualsin73householdsinPittsburg Pennsylvaniawhoweregivenfreecomputersandinternetservicein1995 Theparticipantsansweredaseriesofquestionsatthebeginningofthestudyandeitheroneort