Copyright©2009CengageLearning2.1ChapterTwoGraphicalandTabularDescriptiveTechniquesCopyright©2009CengageLearning2.2Introduction&Re-cap…Descriptivestatisticsinvolvesarranging,summarizing,andpresentingasetofdatainsuchawaythatusefulinformationisproduced.Itsmethodsmakeuseofgraphicaltechniquesandnumericaldescriptivemeasures(suchasaverages)tosummarizeandpresentthedata.DataStatisticsInformationCopyright©2009CengageLearning2.3Populations&SamplesThegraphical&tabularmethodspresentedhereapplytobothentirepopulationsandsamplesdrawnfrompopulations.PopulationSampleSubsetCopyright©2009CengageLearning2.4Definitions…Avariableissomecharacteristicofapopulationorsample.E.g.studentgrades.Typicallydenotedwithacapitalletter:X,Y,Z…Thevaluesofthevariablearetherangeofpossiblevaluesforavariable.E.g.studentmarks(0..100)Dataaretheobservedvaluesofavariable.E.g.studentmarks:{67,74,71,83,93,55,48}Copyright©2009CengageLearning2.5TypesofData&InformationData(atleastforpurposesofStatistics)fallintothreemaingroups:IntervalDataNominalDataOrdinalDataCopyright©2009CengageLearning2.6IntervalData…Intervaldata•Realnumbers,i.e.heights,weights,prices,etc.•Alsoreferredtoasquantitativeornumerical.ArithmeticoperationscanbeperformedonIntervalData,thusitsmeaningfultotalkabout2*Height,orPrice+$1,andsoon.Copyright©2009CengageLearning2.7NominalData…NominalData•Thevaluesofnominaldataarecategories.E.g.responsestoquestionsaboutmaritalstatus,codedas:Single=1,Married=2,Divorced=3,Widowed=4Thesedataarecategoricalinnature;arithmeticoperationsdon’tmakeanysense(e.g.doesWidowed÷2=Married?!)Nominaldataarealsocalledqualitativeorcategorical.Copyright©2009CengageLearning2.8OrdinalData…OrdinalDataappeartobecategoricalinnature,buttheirvalueshaveanorder;arankingtothem:E.g.Collegecourseratingsystem:poor=1,fair=2,good=3,verygood=4,excellent=5Whileitsstillnotmeaningfultodoarithmeticonthisdata(e.g.does2*fair=verygood?!),wecansaythingslike:excellent>poororfair
