In general, statistics is a study of data: describing properties of the data, which is called descriptive statistics, and drawing conclusions about a ...SkiptomaincontentContributorLearningObjectivesTolearnthebasicdefinitionsusedinstatisticsandsomeofitskeyconcepts.Webeginwithasimpleexample.TherearemillionsofpassengerautomobilesintheUnitedStates.Whatistheiraveragevalue?Itisobviouslyimpracticaltoattempttosolvethisproblemdirectlybyassessingthevalueofeverysinglecarinthecountry,addupallthosevalues,thendividebythenumberofvalues,oneforeachcar.Inpracticethebestwecandowouldbetoestimatetheaveragevalue.Anaturalwaytodosowouldbetorandomlyselectsomeofthecars,say\(200\)ofthem,ascertainthevalueofeachofthosecars,andfindtheaverageofthose\(200\)values.Thesetofallthosemillionsofvehiclesiscalledthepopulationofinterest,andthenumberattachedtoeachone,itsvalue,isameasurement.Theaveragevalueisaparameter:anumberthatdescribesacharacteristicofthepopulation,inthiscasemonetaryworth.Thesetof\(200\)carsselectedfromthepopulationiscalledasample,andthe\(200\)numbers,themonetaryvaluesofthecarsweselected,arethesampledata.Theaverageofthedataiscalledastatistic:anumbercalculatedfromthesampledata.Thisexampleillustratesthemeaningofthefollowingdefinitions.Definitions:populationsandsamplesApopulationisanyspecificcollectionofobjectsofinterest.Asampleisanysubsetorsubcollectionofthepopulation,includingthecasethatthesampleconsistsofthewholepopulation,inwhichcaseitistermedacensus.Definitions:measurementsandSampleDataAmeasurementisanumberorattributecomputedforeachmemberofapopulationorofasample.Themeasurementsofsampleelementsarecollectivelycalledthesampledata.Definition:parametersAparameterisanumberthatsummarizessomeaspectofthepopulationasawhole.Astatisticisanumbercomputedfromthesampledata.Continuingwithourexample,iftheaveragevalueofthecarsinoursamplewas\($8,357\),thenitseemsreasonabletoconcludethattheaveragevalueofallcarsisabout\($8,357\).Inreasoningthiswaywehavedrawnaninferenceaboutthepopulationbasedoninformationob