Block 23 Sampling - Theory 13
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Transcript of Block 23 Sampling - Theory 13
Construction QC QA Sampling 1
Quality Control / Quality Assurance
Sampling for Quality Control
Senior/GraduateHMA Course
Construction QC QA Sampling 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 3
Reasons for Sampling Materials
1 . Certification or Source Approval
2 . Process/Quality Control
3 . Acceptance
4 . Independent Verification Samples
Construction QC QA Sampling 4
Types of Sampling
1 . Judgment Sampling
2 . Quota Sampling
3 . Systematic Sampling
4 . STRATIFIED SAMPLING
5 . RANDOM SAMPLING
Construction QC QA Sampling 5
Lot or Population
Construction QC QA Sampling 67-4
Sample from a Lot
Specimen 1 Specimen 3
Specimen 2
Construction QC QA Sampling 7
Random Locations
x Biased Locations
Sampling Location
Construction QC QA Sampling 8
Random
Versus
StratifiedRandom
Random Sampling
Construction QC QA Sampling 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 tables
Construction QC QA Sampling 10
ROADWAY LOT
RANDOM SAMPLING
With simple random Sampling, All samplescould end Up in one
section of a Roadway lot
Construction QC QA Sampling 11
Stratified Random Sampling
Sublot 1
Sublot 2
Sublot 3
Sublot 4
Sta100
Sta110
Sta120
Sta130
Sta140
Construction QC QA Sampling 12
Sampling Roadway Location Example
LOT Size: 4000 LF
Pavement Width: 12 FT
4 Sample Cores per LOT
LOT begins at Sta 100+00
Construction QC QA Sampling 13
Sublot 1
Sublot 2
Sublot 3
Sublot 4
Sta100
Sta110
Sta120
Sta130
Sta140
LOT
Construction QC QA Sampling 14
Sublot 1- Sample Location
Longitudinal (X)
Transverse (Y)
Construction QC QA Sampling 15
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 41
Sublot 1
Sublot 2
Sublot 3
Sublot 4
RANDOM NUMBERTABLE
Construction QC QA Sampling 16
Sublot 1Coordinate X = .74 x 1000 = 740 FTCoordinate Y = .29 x 12 = 3.5 FT.
740 Feet
3.5 Feet
12 FT
1000 Feet
Construction QC QA Sampling 17
Sublot 2
Coordinate X = 0.60 x 1000 = 600 FT
Coordinate Y = 0.21 x 12 = 2.5 FT
Construction QC QA Sampling 18
Stratified Random Sampling
Sublot 1
Sublot 2
Sublot 3
Sublot 4
Sta100
Sta110
Sta120
Sta130
Sta140
Construction QC QA Sampling 19
Stratified Random SamplingSample Location
Sublot 1
Sublot 2
Sublot 3
Sublot 4
3.5’ 2.5’
9.4’
0.1’
107+40 116+00 120+10 132+70
Construction QC QA Sampling 20
Sampling at the HMA PlantExample 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 sequence
Construction QC QA Sampling 21
Select Sublots
• From a random number generator you got the following:
0.37
0.90
0.66
0.67
0.68
Construction QC QA Sampling 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 23
Questions?