统计学第四章.ppt

DescribingData:

DisplayingandExploringDataChapter4

GOALSDevelopandinterpretadotplot.Developandinterpretastem-and-leafdisplay.Computeandunderstandquartiles,deciles,andpercentiles.Constructandinterpretboxplots.Computeandunderstandthecoefficientofskewness.Drawandinterpretascatterdiagram.Constructandinterpretacontingencytable.2

DotPlotsAdotplotgroupsthedataaslittleaspossibleandtheidentityofanindividualobservationisnotlost.Todevelopadotplot,eachobservationissimplydisplayedasadotalongahorizontalnumberlineindicatingthepossiblevaluesofthedata.Ifthereareidenticalobservationsortheobservationsaretooclosetobeshownindividually,thedotsare“piled”ontopofeachother.3

DotPlots-ExamplesReportedbelowarethenumberofvehiclessoldinthelast24monthsatSmithFordMercuryJeep,Inc.,inKane,Pennsylvania,andBrophyHondaVolkswageninGreenville,Ohio.Constructdotplotsandreportsummarystatisticsforthetwosmall-townAutoUSAlots.4

DotPlot–MinitabExample5

Stem-and-LeafInChapter2,weshowedhowtoorganizedataintoafrequencydistribution.Themajoradvantagetoorganizingthedataintoafrequencydistributionisthatwegetaquickvisualpictureoftheshapeofthedistribution.Onetechniquethatisusedtodisplayquantitativeinformationinacondensedformisthestem-and-leafdisplay.Stem-and-leafdisplayisastatisticaltechniquetopresentasetofdata.Eachnumericalvalueisdividedintotwoparts.Theleadingdigit(s)becomesthestemandthetrailingdigittheleaf.Thestemsarelocatedalongtheverticalaxis,andtheleafvaluesarestackedagainsteachotheralongthehorizontalaxis.Advantageofthestem-and-leafdisplayoverafrequencydistribution-theidentityofeachobservationisnotlost.6

Stem-and-Leaf–ExampleSupposethesevenobservationsinthe90upto100classare:96,94,93,94,95,96,and97.Thestemvaluei