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ACCEPTANCE SAMPLING TECHNIQUE
OPERATION MGMT
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ACCEPTANCE SAMPLING TECHNIQUE
1.
USEFUL WHEN 100% INSPECTION IS NOT PRACTICAL
2.
ACCEPTANCE SAMPLING IS THE BEST WAY OF ESTIMATING THE QUALITY OF INCOMING OR
OUTGOING LOTS
3.
RANDOM SAMPLING PROVIDES EACH ELEMENT
WITH AN EQUAL OF BEING SELECTED AND ALLOWS LOGICAL INTERPRETATION TO BE
MADE ABOUT THE LOT.
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ACCEPTANCE SAMPLING INSPECTION :
1.
SAMPLING
BYATTRIBUTES
2.
SAMPLING BY VARIABLES
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APPLICATION OF ACCEPTANCE SAMPLING
1.
TESTING IS DESTRUCTIVE
2.
COST OF INSPECTION OF WHOLE LOT IS VERY HIGH
3.
INSPECTION OF WHOLE LOT IS NOT POSSIBLE
4.
WHEN INSPECTION ERROR RATE IS SO HIGH THAT 100% INSPECTION MIGHT PASS A
HIGHER PERCENTAGE OF DEFECTIVE UNITS AS COMPARED TO SAMPLING PLANS
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ACCEPTANCE SAMPLING BY ATTRIBUTE
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INVOLVES EXTRACTING A RANDOM SAMPLE FROM THE LOT TO DETERMINE WHETHER TO
ACCEPT OR REJECT THE ENTIRE LOT ON THE BASIS OF THE SAMPLE OR SEPARATE THE GOOD
FROM THE BAD
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THIS PROCESS MAY BE USED :
1.
INWARD GOODS
2.
RECEIVING INSPECTION
3.
OR COMPONENTS
4.
IN PROCESS OF INSPECTION FOR SEMI FINSHED GOODS
5. FINISHED PRODUCT
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ACCEPTANCE SAMPLING BY ATTRIBUTE
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THE SAMPLE MAY BE :
1.
SINGLE SAMPLE PLAN: A SINGLE SAMPLE OUT OF SPECIFIED LOT IS TAKEN. ALL THE
ITEMS OF THE SAMPLE ARE PHYSICALLY INSPECTED AND DEFECTIVES ARE NOTED DOWN AND
IT IS COMPARED WITH TOLERANCE LIMIT. IF DEFECTIVES ARE UP TO TOLERANCE LIMIT
THE LOT IS ACCEPTED AND OTHERWISE REJECTED.
2.
DOUBLE SAMPLING PLAN:-TWO POSSIBILITIES EITHER ACCEPT OR REJECT. IF THE
RESULT OF SINGLE SAMPLE IS INCONCLUSIVE THEN A SECOND SAMPLE IS DRAWN. THE
RESULT OF SECOND SAMPLE IS COMBINED WITH SECOND SAMPLE TO REACH A FINAL
3.
SEQUENTIAL SAMPLING :-
1.
UNITS ARE RANDOMLY SELECTED FROM THE LOT
2.
TESTED ONE BY ONE
3.
AFTER EACH ONE IS TESTED A REJECT ,ACCEPT OR CONTINUOUS SAMPLING DECISION IS
TAKEN, THIS PROCESS CONTINUES UNTIL THE LOT IS ACCEPTED OR REJECTED
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IMPORTANT
CONCEPT OF ACCEPTANCE SAMPLING BY ATTRIBUTE
1.
AVERAGE OUTGOING QUALITY CURVES
2.
OPERATING CHARACTERISTICS CURVES
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AVERAGE OUTGOING QUALITY CURVES
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ACCEPTANCE SAMPLING PLANS PROVIDE MANAGERS WITH THE ASSURANCE THAT THE
AVERAGE QUALITY LEVEL OR PERCENT DEFECTIVE ACTUALLY GOING TO CUSTOMER WILL NOT
EXCEED A CERTAIN LIMIT
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OPERATING CHARACTERSTICS (OC) CURVES
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WHEN WE GO FOR ACCEPTANCE SAMPLING PLANS
1.
WE ACCEPT GOOD LOTS
2.
WE REJECT BAD LOTS
3.
WE MAY ACCEPT BAD LOTS
4.
WE MAY REJECT GOOD LOTS
§ WHEN A GOOD LOT IS REJECTED THE ERROR IS KNOWN
AS TYPE ONE ERROR AND THE RISK OF REJECTING A GOOD LOT BASED ON SAMPLE EVIDENCE
IS KNOWN AS PRODUCER’S RISK
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WHEN A BAD LOT IS ACCEPTED AS GOOD LOT BASED ON
SAMPLE EVIDENCE THE ERROR IS KNOWN AS TYPE TWO ERROR. ALSO KNOWN AS
CONSUMER’S RISK
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THE OPERATING CHARACTERISTICS CURVE DESCRIBES AN IMPORTANT FEATURE OF
ACCEPTANCE SAMPLING PLAN. IT SHOWS HOW WELL AN ACCEPTANCE SAMPLING PLAN
DISCRIMINATES BETWEEN GOOD OR BAD
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OPERATING CHARACTERISTICS CURVE
• D
1. WE
DEFINE A BAD LOT AS ANY HAVING 5% OR MORE DEFECTIVE IS KNOWN AS LOT TOLERANCE
PERCENT DEFECTIVE
2. THE
PROBABILITY OF ACCEPTING A LOT WITH 5% DEFECTIVE SHOULD BE AS LOW AS POSSIBLE
10% THAT IS CALLED THE CONSUMER RISK. BUT THE PROBABILITY OF REJECTING A LOT
WITH 5% DEFECTIVE OR MORE IS 90%
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