3 About the area below the curve
Thetotalareabelowthecurverepresentsthatalltheworkpiecesfallwithinthedistributionrange.InFig.6.27,pointCrepresentstheminimumdimensionAmin,zoneCDrepresentsthetolerancerange，theareabelowpointCandDrepresentsthequalifiedpartsratio,andtheareaoftheleftpartbelowthecurve(nohatchedpart)istherejectedratio.Whenthedimensionisthediameterofanexternalcylindricalpart,theleftnon-hatchedpartcannotberepaired,therighthatchedpartcanberepaired.Itisexactlycontrarywiththeholemachining.TheareafromαtoXcanbecalculatedwiththefollowingformulaforanormaldistribution
1A??YdX???2?x?e?(X??)22?2dX
