STATstatisticsinpractice•WithourcountrytakingpartinWTO，ourcompaniesarefacingextraordinarilyseriouschallenges，particularlyinAutomobileIndustry。Itisnotonlychallenge，butalsotheopportunity。Inordertoacceptthechallenges，nationalAutomobileIndustry，insuccession，takelotsofmeasurestoreplyit。AautogroupcarriedthroughaseriesofimprovementsonenginesystemonA1modelcar。Eventually，itincreasesthespeedofstartupandknocksdownthenoises，renamedbyA2。Duringthis，onemomentousissuethatcompanypaidattentiontoisenergyefficientofcars。Savinggasisbigsalepoint。TheA1carthatunimprovedcostrelativelyhighvolumegas，8。48literperonehundredkilometers。Thecompanywishthatimprovedcarscansavethegasthantheformercars，atleast，notcostmorethanbefore。Chapter8HypothesisTestingSTATChapter8Statisticsinpractice•Therefore，takeout15A2autosrandomlytodoexperiment，getthestatisticsthat15carscostthevolumeofgasper100kilometers。Seethefollowingchart：（15autosconsumethevolumeofgasper100kilometers）unit：liter8.508.758.338.218.528.308.318.198.408.868.418.018.208.268.39Theaverageis8.377.accordingtothisstatistics,themanagerofTechnologyApartmentconfirmthatimprovedautoscansavethegas.STAT•ThemanagerofQualityApartmenthasdifferentideaaboutthisconclusion.Hethoughtthatthephenomenoncomefromtherandomsample.Itissoearlytoperoratethatimprovedautosincreasethemeanmiles-per-gallonratingandweshoulddoHypothesisTestingonstatistics.EngineerZhangwhohaspassedthepractitionerqualificationfromtheQualityApartmenthaslearntalotofstatisticsmethods.ThemanagerofQualityApartmentaskedEngineerZhangtosolvethisproblem.Throughsimplecalculation,theEngineerZhanggottheconclusionthatthepresentdatacannotfiguretheautosbeforeandafterimprovedhavenodistinctchangesinmiles-per-gallonrating.Therefore,howEngineerZhangtogetthisconclusion?Chapter8StatisticsinpracticeSTAT•ThekeystoneofchapterThekeystoneofchapter•1、thebasictheoryofHypothesisTesting•2、theformandkindofHypothesisTesting；•3、typeIandtypeIIerror；•4、IntervalTestingandmethodsofHypothesisTes...
