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1、STANDARDDEVIATION*Standarddeviationcantypicallybedescribedasthedeviationapieceofdatediffersfromthemean.*Standarddeviationcanalmostbedescribedasthe“meanofthemean”itisaformofstatisticalanalysis*YoudothiswhenyouhavedatathatisdistributednormallyorNormaldistribution.This
2、meansthatthepiecesofdatadon’tdifferfromthemeaninextremes.*Standarddeviationusespasthistoryordatatoextrapolatefutureevents.Itshowsthetendencyofthedataandhowitisspreadout.(--Subtractedfromthemean--+-----addedtothemean------)*Thisisknownasabellcurve.Thelinethroughthemi
3、ddlerepresentsthemeanoraverageofthedata.EachsectionisapercentofthedataandisonestandarddeviationawayfromthemeanRed-theredmakesup68%oftheentiredata;eachhalfisonly34%.(Mostofthedatafallsinthiscategory)Green-eachhalfofthegreenis14%makingthegreenatotalof28%butaddedtother
4、edmakesupforapproximately95%ofthedata.Blue-Bluerepresent2%eachbutaddedtothetotalamountitis99%(almostalldatainthissectionwouldbeoutliers)White-averysmallpercentoftennotrecognizedaspartofthedata(anythinginthissectionwouldbeanextremeoutlier)FractionNumberofStandardOfDa
5、taDeviationsfromMean50.0%.67468.31.00090.01.64595.01.96095.42.00098.02.32699.02.57699.73.000*Thisshowsthepercentofthedatawillfallinhowmanystandarddeviations*Mostofthedataisfoundwithinthefirsttwostandarddeviationsawayfromthemeannegativeorpositive*Thewiderandlowerbell
6、curvesrepresentahigherstandarddeviationamount*Asteepermorecondensedcurverepresentsasmallerstandarddeviationamountandthedataismoreclusteredaroundthemean*Oneformofcalculatinganaverageisthemean.*ThemeanisthesumofallthepiecesofdatadividedbythetotalnumberofpiecesofdataMe
7、an=SumofdataTotal#piecesofdataEx.5,6,7,5,6,4,8,9SumofdataTotal#piecesofdata508Mean=6.25*OneequationtodeterminethestandarddeviationisS=StandardDeviationå=ThesumofthepiecesofdataX=yourpieceofdataM=meanN=yournumberofpiecesofdata*Howeverallthisseemsverycomplicatingtofin
8、dofstandarddeviationwhenthereisaneasierwaytodoit*YouwillneedseveralpiecesofdatatodeterminethemeanEx.5,7,4,9,5,7,6,4,8,5Sonowyouneedtocalcu
