In general, statistics is a study of data: describing properties of the data, which is called descriptive statistics, and drawing conclusions about a population of ...PreviousSectionTableofContentsNextSection1.1BasicDefinitionsandConceptsLearningObjectiveTolearnthebasicdefinitionsusedinstatisticsandsomeofitskeyconcepts.Webeginwithasimpleexample.TherearemillionsofpassengerautomobilesintheUnitedStates.Whatistheiraveragevalue?Itisobviouslyimpracticaltoattempttosolvethisproblemdirectlybyassessingthevalueofeverysinglecarinthecountry,addingupallthosenumbers,andthendividingbyhowevermanynumbersthereare.Instead,thebestwecandowouldbetoestimatetheaverage.Onenaturalwaytodosowouldbetorandomlyselectsomeofthecars,say200ofthem,ascertainthevalueofeachofthosecars,andfindtheaverageofthose200numbers.Thesetofallthosemillionsofvehiclesiscalledthepopulationofinterest,andthenumberattachedtoeachone,itsvalue,isameasurement.Theaveragevalueisaparameter:anumberthatdescribesacharacteristicofthepopulation,inthiscasemonetaryworth.Thesetof200carsselectedfromthepopulationiscalledasample,andthe200numbers,themonetaryvaluesofthecarsweselected,arethesampledata.Theaverageofthedataiscalledastatistic:anumbercalculatedfromthesampledata.Thisexampleillustratesthemeaningofthefollowingdefinitions.DefinitionApopulationAllobjectsofinterest.isanyspecificcollectionofobjectsofinterest.AsampleTheobjectsexamined.isanysubsetorsubcollectionofthepopulation,includingthecasethatthesampleconsistsofthewholepopulation,inwhichcaseitistermedacensus.DefinitionAmeasurementAnumberorattributecomputedforeachmemberofasetofobjects.isanumberorattributecomputedforeachmemberofapopulationorofasample.ThemeasurementsofsampleelementsarecollectivelycalledthesampledataThemeasurementsfromasample..DefinitionAparameterAnumberthatsummarizessomeaspectofthepopulation.isanumberthatsummarizessomeaspectofthepopulationasawhole.AstatisticAnumbercomputedfromthesampledata.isanumbercomputedfromthesampledata.Continuingwithourexample,iftheaveragevalueofthecar