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1、StatisticalAnalysisofWaterQualityDatafromLakeCaseyandSilverLakeMarkD.EckerAssistantProfessorDepartmentofMathmaticsAaronJanssenUndergraduateStudentDepartmentofEarthSciencesUNISummerLakesStudyReportAugust7,20006IntroductionTheUniversityofNorthernIowaSummerLakesProj
2、ectiscomposedofamutlidisciplinedteamofscientistsstudyingwaterqualityintwoIowalakesduringthesummersof1999and2000.Duringtheinitialsummer,ateamofnineUniversityofNorthernIowafacultyand14studentsmonitoredwaterqualityvariablesatLakeCaseyinTamacountyandSilverLakenearDel
3、hi,Iowa.Numerouswaterqualityvariablessuchasdissolvedoxygen,phosphorusconcentrations,chlorophyllalevels,surfacewatertemperaturewerecollectedonnineseparateoccasionsineachlake.Thegoalofthispaperistoprovideastatisticalanalysisofthefinal1999waterqualitydataset.Weshall
4、provideaspatialandspatio-temporalanalysisofdissolvedphosphorusasafunctionoftheotherwaterqualityvariables.Apurelyspatialanalysisrevolvesaroundtheassumptionthat,forafixedtimepoint,responses(phosphoruslevels)atpairsofsitescloserinspacetendtobemoresimilarthantherespo
5、nsesatpairsofsitesfurtherapart.Wealsowillexplorefortemporalautocorrelation;namely,dissolvedphosphoruslevelsataparticularsitetendtobemoresimilarifseparatedbyshortertimesintervals(daysorweeksratherthanmonths).Thepaperisorganizedasfollows:Section2providesapreliminar
6、yanalysisofthedatawhilesection3discussesthepurelyspatialanalysisforseveralfixedtimepoints.Section4outlinesthespatio-temporalanalysiswhileconclusionsarepresentedinsection5.I.PreliminaryAnalysesWaterqualityvariables,dissolvedoxygen,totalanddissolvedphosphorus,surfa
7、cewatertemperatureandchlorophyllawereregularlymeasuredatmostsitesinbothlakesoverthesummerof1999.Othervariables,suchasnitrate,cyanazineandatrazinelevelsweremeasuredlessregularly;onlyatsomesitesandcertaintimes.AtSilverlake,20sitesweresampledonMay28,July8andAugust2,
8、1999andasubsetofapproximately10sitesonJune22and29,July12,19and26andAugust9,1999.Figure1showsall20sitessampledatSilverLake.AtLakeCasey,waterqualityvariableswere
