Cut-off　rules　specialized　in　sequential　observation　and　selection　problem.　The　established　cutoff　rules　decreased　the　cutoff　value　for　low　risk　in　repetitive　applications　context.　Furthermore,　the　decreasing　of　cutoff　value　can　maximize　the　average　profit　which　cost　is　reducing　the　number　of　observation　and　enhancing　the　uncertainty　of　decision.　In　this　paper,　reducing　the　benchmark　is　more　efficient　than　decreasing　cutoff　value　in　risk　aversion.　The　established　cut-off　rule　had　been　revised　and　the　results,　based　on　the　simulations,　indicate　that　the　revised　cut-off　rule　is　risk　aversion　and　has　better　average　profit.　The　prove　process　that　the　20　percent　is　the　approximate　optimal　proportion　bring　this　paper　to　a　close.