What-is-Statistics

WhatisStatistics?Chapter11-2GOALS1.Understandwhywestudystatistics.2.Explainwhatismeantbydescriptivestatisticsandinferentialstatistics.3.Distinguishbetweenaqualitativevariableandaquantitativevariable.4.Describehowadiscretevariableisdifferentfromacontinuousvariable.5.Distinguishamongthenominal,ordinal,interval,andratiolevelsofmeasurement.1-3IntroductionMorethan100yearsagoH.G.Wells,anEnglishauthorandhistorian,suggestedthatonedayquantitativereasoningwillbeasnecessaryforeffectivecitizenshipastheabilitytoread.Oneofthetoolsusedtomakedecisionsisstatistics.Statisticsisusednotonlybybusinesspeople;weallalsoapplystatisticalconceptsinourlives.1-4Introduction(cont.)Asastudentofbusinessoreconomics,youwillneedbasicknowledgeandskillstoorganize,analyze,andtransformdataandtopresenttheinformation.Inthistext,wewillshowyoubasicstatisticaltechniquesandmethodsthatwilldevelopyourabilitytomakegoodpersonalandbusinessdecisions.1-5WhyStudyStatistics?Thefirstreasonisthatnumericalinformationiseverywhere.–In2005thetypicalhouseholdincomeintheUnitedStateswas$46,326.ForhouseholdsintheNortheastthetypicalincomewas$50,882,$45,950intheMidwest,$42,138intheSouth,and$50,002intheWest.Youcancheckthelatestinformationbygoingto(cont.)–Fortheyear2006Boeing(波音公司）reportedtheysold1058aircraft.Thetableshowsthesalesbytypeofaircraft.1-7WhyStudyStatistics?(cont.)–USAToday（今日美国杂志）()prints“Snapshots”（快照）thataretheresultofsurveysconductedbyvariousresearchorganizations（研究组织）,foundations（基金会）,andthefederalgovernment（联邦政府）.1-8WhyStudyStatistics?(cont.)Asecondreasonfortakingastatisticscourseisthatstatisticaltechniquesareusedtomakedecisionsthataffectourdailylives.Thatis,theyaffectourpersonalwelfare.–Insurancecompaniesusestatisticalanalysistosetratesforhome,automobile,life,andhealthinsurance.–TheEnvironmentalProtectionAgencyisinterestedinthewaterqualityofLakeErie（伊利湖）aswellasotherlakes.Theyperiodicallytakewatersamplestoestablishthelevelofcontaminationandmaintainthelevelofwaterquality.–1-9WhyStudyStatistics?(cont.)–Medicalresearchersstudythecureratesfordiseasesusingdifferentdrugsanddifferentformsoftreatment.Athirdreasonfortakingastatisticscourseisthattheknowledgeofstatisticalmethodswillhelpyouunderstandhowdecisionsaremadeandgiveyouabetterunderstandingofhowtheyaffectyou.1-10WhyStudyStatistics?(cont.)Nomatterwhatlineofworkyouselect,youwillfindyourselffacedwithdecisionswhereanunderstandingofdataanalysisishelpful.Inordertomakeaninformeddecision,youwillneedtobeableto:1.Determinewhethertheexistinginformationisadequateoradditionalinformationisrequired.2.Gatheradditionalinformation,ifitisneeded,insuchawaythatitdoesnotprovidemisleadingresults.1-11WhyStudyStatistics?(cont.)–3.Summarizetheinformationinausefulandinformativemanner.–4.Analyzetheavailableinformation.–5.Drawconclusionsandmakeinferenceswhileassessingtheriskofanincorrectconclusion.Thestatisticalmethodspresentedinthetextwillprovideyouwithaframeworkforthedecision-makingprocess.1-12WhatisMeantbyStatistics?Itreallyhastwomeanings.–Inthemorecommonusage,statisticsreferstonumericalinformation（统计数据）.–Examplesincludetheaveragestartingsalaryofcollegegraduates,thenumberofdeathsduetoalcoholism（酗酒）lastyear,thechangeintheDowJones（道琼斯）IndustrialAveragefromyesterdaytotoday,andthenumberofhomerunshitbytheChicagoCubsduringthe2007season.–Intheseexamplesstatisticsareavalueorapercentage.1-13WhatisMeantbyStatistics?Acollectionofnumericalinformationiscalledstatistics（统计数据）(plural).–examplesinclude:–ThetypicalautomobileintheUnitedStatestravels11,099milesperyear,thetypicalbus9,353milesperyear,andthetypicaltruck13,942milesperyear.InCanadathecorrespondinginformationis10,371milesforautomobiles,19,823milesforbuses,and7,001milesfortrucks.–Themeantimewaitingfortechnicalsupportis17minutes.–Themeanlengthofthebusinesscyclesince1945is61months.Theaboveareallexamplesofstatistics.1-14presentingstatisticalinformationinagraphicalformAgraphisusefulforcapturingreaderattentionandportrayingalargeamountofinformation.1-15presentingstatisticalinformationinagraphical图1-1菲多利公司点心和薯片类产品在美国超市中的销售量与市场份额1-16WhatisMeantbyStatistics?Statisticsisthescienceofcollecting,organizing,presenting,analyzing,andinterpretingnumericaldatatoassistinmakingmoreeffectivedecisions.1-17WhoUsesStatistics?Asthedefinitionsuggests,thefirststepininvestigatingaproblemistocollectrelevantdata.Theymustbeorganizedinsomewayandperhapspresentedinachart,suchasChart1–1.Onlyafterthedatahavebeenorganizedarewethenabletoanalyzeandinterpretthem.1-18WhoUsesStatistics?Herearesomeexamplesoftheneedfordatacollection.–ResearchanalystsforMerrillLynch（美林证券）evaluatemanyfacetsofaparticularstockbeforemakinga“buy”or“sell”recommendation.Theycollectthepastsalesdataofthecompanyandestimatefutureearnings.Otherfactors,suchastheprojectedworldwidedemandforthecompany’sproducts,thestrengthofthecompetition,andtheeffectofthenewunion–managementcontract（联合经营合同）,arealsoconsideredbeforemakingarecommendation.1-19WhoUsesStatistics?Themarketingdepartment