105StorageTimeExample

105StorageTimeExample - TWO-FACTOREXPERIMENT storage.,/mL...

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Unformatted text preview: EXAMPLEANALYSISOFANUNBALANCED TWO-FACTOREXPERIMENT Anexperimentwasconductedtostudytheeffectofstoragetimeandstorage temperatureontheamountofactiveingredientpresentinadrugattheendof storage.Sixteenvialsofthedrug,eachcontainingapproximately30mg/mL ofactiveingredient,wereassigned(usingacompletelyrandomizeddesign) tothefollowingtreatments: 1. Storagefor3monthsat20 ◦ C 2. Storagefor3monthsat30 ◦ C 3. Storagefor6monthsat20 ◦ C 4. Storagefor6monthsat30 ◦ C Sixofthe16vialsweredamagedduringshipmenttothelaboratorywherethe activeingredientwasmeasured.Accuratemeasuresoftheamountofactive ingredientcouldbeobtainedonlyforthe10undamagedvials.Thetable belowshowstheamountofactiveingredientlostduringstorage(intenthsof mg/mL)foreachoftheundamagedvials. Copyright c 2011Dept.ofStatistics(IowaStateUniversity) Statistics511 1/1 StorageTemperature StorageTime 20 ◦ C 3 ◦ C 3months 25 91215 6months 6677 16 Wecallanexperiment balanced ifalltreatmentshavethesame numberofexperimentalunits.Althoughthisexperimentwasdesigned tobebalancedwith4experimentalunitspertreatment,ithasbecome unbalanced becausethenumberofmeasuredexperimentalunits varieswithtreatment. Copyright c 2011Dept.ofStatistics(IowaStateUniversity) Statistics511 2/1 Analysisofunbalancedfactorialstudies Ourdiscussionfocuseson2wayfactorials,issuessamefor > 2way Whendesignisbalanced, lotsofnicethingshappen → simpleanalysis Whenunbalanced,needtoeither: thinkcarefullyaboutwhatyou’redoing or,knowwhathappensbydefault. Makesureyou’regettingwhatyoureallywant. Thefollowingshouldbeareviewof500/402. Ifnot,gethelpinofficehours. OurapproachtounbalancedANOVAisthegenerallyaccepted approachintheUS.Sometimescalled“theSASapproach”. Notuniversal.UKusers,especiallyJohnNelderdiffer.Nelderhad ahugeinfluenceonR. Mosteasilyexplainedintermsofacellmeansparameterization. Copyright c 2011Dept.ofStatistics(IowaStateUniversity) Statistics511 3/1 2wayfactorial,terminology,cellmeansparam. StorageTemperature StorageTime...
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This note was uploaded on 02/11/2012 for the course STAT 511 taught by Professor Staff during the Spring '08 term at Iowa State.

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105StorageTimeExample - TWO-FACTOREXPERIMENT storage.,/mL...

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