SAMPLING

By ARUN SHARMAB.Sc. (chemistry)

INTRODCTION OF SAMPLING

SAMPLING IS VERY OFTEN USED IN OUR DAILY LIFE.FOR EXAMPLE WHILE PURCHASING FOOD GRAINS FROM A SHOP WE USUALLY EXAMINE A HANDFUL FROM A BAG TO THE ASSES THE QUALITY OF THE COMMODITY. A DOCTOR EXAMINES A FEW DROP OF BLOOD AS SAMPLE AND DRAWS CONCLUSION ABOUT BLOOD CONSTITUTION OF THE WHOLE BODY. THUS MOST OF INVESTIGATIONS ARE BASED ON SAMPLE.

SAMPLING IS THE SCIENCE OF EXTRACTING FROM A LARGER QUANTITY OF MATERIAL, A SMALL PORTION WHICH IS TRULY REPRESENTATIVE OF THE BULK MATERIAL. A REPERSENTATIVE SAMPLE IS ONE WHICH HAS ESSENTIALLY THE SAME PHYSICAL AND CHEMICAL CHARACTERISTICS.

WHAT IS SAMPLING ?

Cont..

A SAMPLE IS SOME PART OF A LARGER BODY SPECIALLY SELECTED TO REPRESENT THE WHOLE.

SAMPLING THEN IS TAKING ANY PORTION OF A POPULATION OR UNIVERSE AS REPRESENTATIVE OF THAT POPULATION OR UNIVERSE.

SAMPLING IS THE PROCESS BY WHICH THIS PART IS CHOSEN.

AIM OF SAMPLING

JUDGING ACCEPTIBILITY : FOR THE PURCHASE OR SELL OF MATERIALS OR GOODS, SPECIFICATIONS ARE MENTIONED. SAMPLING HEPLS TO DETERMINE WHETHER THESE REQUIREMENT ARE FULFILLED.DETECTION OF CONTAMINATION: SAMPLING IS TO ASSURE THAT THE MATERIAL IS FREE FROM CONTAMINATION.IDENTIFICATION AND ESTIMATION OF MATERIAL: SAMPLING HELPS IN IDENTIFICATION AND ESTIMATING IN VARIOUS MATERIAL PRESENT IN UNIVERSE.

FACTORS INVOLVED IN SAMPLING

NATURE OF THE BULK MATERIAL AND ITS HOMOGENEITY: IF THE MATERIAL IS HOMOGENEOUS THEN SAMPLING IS EASY AND EVEN A SMALL SAMPLE WILL GIVE AN ACCURATE PICTURE OF THE COMPOSITION WHOLE MATERIAL.

EXPECTED ACCURACY OF THE RESULT: ACCURACY SHOULD BE VERY HIGH FOR VITAL ANALYSIS.

COST AND TIME OF ANALYSIS: THE TIME REQUIRED FOR SAMPLING SHOULD NOT BE VERY LONG AND THE COST OF SAMPLING SHOULD NOT BE MORE THAN COST OF PRODUCT.

IMPORTANCE OF GOOD SAMPLING

SHOULD BE A TRUE REPRESENTATIVE OF THE UNIVERSE SHOULD BE POSSIBLE MEASURE OR ESTIMATE SAMPLING ERROR THE RESULT OF SAMPLING STUDY IN GENERAL SHOULD BE APPLICABLE TO THE ENTIRE BULK OF THE MATERIAL THE PHYSICAL CONDITION OF THE TEST MATERIAL IS A VERY IMPORTANT FACTOR TO BE CONSIDERED WHILE SAMPLING THE COST OF THE SAMPLING TESTS SHOULD BE CONSIDERED . THE COST THE SAMPLING ULTIMATELY CHANGES THE COST OF THE PRODUCTS

STAGES OF SAMPLINGBULK MATERIAL

SAMPLING UNITINCERMENT

GROSS SAMPLING

SUB SAMPLING

ANALYSIS SAMPLE

EXPLATION OF IMPORTANT TERMS

UNIVERSE OR POPULATIONSAMPLESAMPLING UNITINCREMENTGROSS SAMPLINGSUB-SAMPLINGANALYSIS SAMPLING

TYPE OF SAMPLING RANDOM SAMPLING NON RANDOM OR SYSTEMATIC

SAMPLING

SAMPLING OF SOLIDS

IT IS OF 2 TYPES: COMPACT SOLID PARTICULATE SOLID

SAMPLING OF LIQUID

IT INVOLVES 3 DIFFERENT CASES: HOMOGENOUS LIQUID HETEROGENEOUS LIQUID FLOWING LIQUID

SAMPLING OF GASES

ITS OF ONLY 1TYPE I.E.: HOMOGENEOUS