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

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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?