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# Block 23 Sampling - Theory 13

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### Block 23 Sampling - Theory 13

1. 1. Senior/Graduate HMA Course Quality Control / Quality Assurance Sampling for Quality ControlConstruction QC QA Sampling 1
2. 2. Requirements For a Sampling and Testing Program 1. Frequency of Tests? 2. Location of Samples? 3. Size of Samples? 7-2 Construction QC QA Sampling 2
3. 3. Reasons for Sampling Materials 1 . Certification or Source Approval 2 . Process/Quality Control 3 . Acceptance 4 . Independent Verification Samples Construction QC QA Sampling 3
4. 4. Types of Sampling 1 . Judgment Sampling 2 . Quota Sampling 3 . Systematic Sampling 4 . STRATIFIED SAMPLING 5 . RANDOM SAMPLINGConstruction QC QA Sampling 4
5. 5. Lot or PopulationConstruction QC QA Sampling 5
6. 6. Sample from a LotSpecimen 1 Specimen 3 Specimen 2 Construction QC QA Sampling 6 7-4
7. 7. Sampling Location  Random Locations x Biased LocationsConstruction QC QA Sampling 7
8. 8. Random SamplingRandom Versus Stratified RandomConstruction QC QA Sampling 8
9. 9. Random Sampling• Any portion of the population has equal chance of being selected• Bias is introduced when judgment is used - Use the tables!• Use random number tablesConstruction QC QA Sampling 9
10. 10. RANDOM SAMPLING With simple random Sampling, All samples could end Up in one section of a Roadway lot ROADWAY LOTConstruction QC QA Sampling 10
11. 11. Stratified Random Sampling Sublot Sublot Sublot Sublot 1 2 3 4Sta Sta Sta Sta Sta100 110 120 130 140Construction QC QA Sampling 11
12. 12. Sampling Roadway Location Example LOT Size: 4000 LF Pavement Width: 12 FT 4 Sample Cores per LOT LOT begins at Sta 100+00Construction QC QA Sampling 12
13. 13. LOT Sublot Sublot Sublot Sublot 1 2 3 4Sta Sta Sta Sta Sta100 110 120 130 140 Construction QC QA Sampling 13
14. 14. Sublot 1- Sample Location Longitudinal (X) Transverse (Y)Construction QC QA Sampling 14
15. 15. RANDOM NUMBER Sublot 2 Sublot 4 TABLE Sublot 1 Sublot 3 74 60 01 27 43 X 29 21 78 01 43 Y 28 37 00 49 97 73 08 87 32 97 72 14 09 70 41Construction QC QA Sampling 15
16. 16. Sublot 1 Coordinate X = .74 x 1000 = 740 FT Coordinate Y = .29 x 12 = 3.5 FT. 740 Feet 12 FT 3.5 Feet 1000 FeetConstruction QC QA Sampling 16
17. 17. Sublot 2Coordinate X = 0.60 x 1000 = 600 FTCoordinate Y = 0.21 x 12 = 2.5 FT Construction QC QA Sampling 17
18. 18. Stratified Random Sampling Sublot Sublot Sublot Sublot 1 2 3 4Sta Sta Sta Sta Sta100 110 120 130 140Construction QC QA Sampling 18
19. 19. Stratified Random Sampling Sample Location 107+40 116+00 120+10 132+70Sublot Sublot Sublot 2 9.4’ 1 4 Sublot3.5’ 2.5’ 3 0.1’Construction QC QA Sampling 19
20. 20. Sampling at the HMA Plant Example Problem• Lot size is 5000 tons• The sub-lot size is 1000 tons• Sublot samples – – Select a block of numbers from the random number table• Calculate the sampling sequenceConstruction QC QA Sampling 20
21. 21. Select Sublots• From a random number generator you got the following: 0.37 0.90 0.66 0.67 0.68Construction QC QA Sampling 21
22. 22. Select Sublots• The next step is to determine which ton you are going to test within the 5000 MG (ton) lot.• The first sample would be at 0.37 * 1000 or 370 MG (tons)• The second sample would be at 0.90 *1000 + 1000 or 1900 MG (tons)• The third sample would be at 0.66 * 1000 + 2000 or 2660 MG (tons)Construction QC QA Sampling 22
23. 23. Questions?Construction QC QA Sampling 23