Procedures and Guidelines for Validating Contractor Test Data (2020) / Chapter Skim
Currently Skimming:
Pages 27-48
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 27... ...
27 C H A P T E R 3 The procedures identified in the project were evaluated using numerical simulations to quantify risks and qualify acceptable procedures. The research approach described in Chapter 2 provided the basis for this evaluation, and SHA data were used to test the effectiveness of the validation procedures.
|
From page 28... ...
28 Procedures and Guidelines for Validating Contractor Test Data 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0% 5% 10% 15% 20% 25% Su cc es s Ra te (% ) SHA sample CVSample 1 size = 7 t_test UV_t_test p_t_test ks_test U_test Figure 11.
|
From page 29... ...
Findings and Applications 29 dotted line in Figures 13 and 14)
|
From page 30... ...
30 Procedures and Guidelines for Validating Contractor Test Data for Scenario 3 where the sample means were unequal while the standard deviations were equal (µ1 ≠ µ2 and s1 = s2) , except for the Ansari-Bradley test that requires that the samples have equal medians showed a lower success rate.
|
From page 31... ...
Findings and Applications 31 Summary of Numerical Analysis Findings The following observations were made based on the numerical simulations conducted on the normally distributed and nonparametric data sets: • The t-test and the Welch's t-test (unequal variance t-test) showed consistent satisfactory results in the simulations at the selected significance level regardless of distribution type.
|
From page 32... ...
32 Procedures and Guidelines for Validating Contractor Test Data (presented in Appendix D)
|
From page 33... ...
Findings and Applications 33 [– log10 (p-value)
|
From page 34... ...
34 Procedures and Guidelines for Validating Contractor Test Data D2S Limits The results of applying D2S limits on split samples from the SHA data are presented in Table 8. As shown, 23.9% of the data sets failed the paired t-test but only 4.5% failed the D2S limits when applied on the same split samples.
|
From page 35... ...
Findings and Applications 35 contractors to perform QC tests on samples split from the same SHA bulk samples used for each lot. A data set comprised of SHA and contractor data from multiple projects was used to illustrate and compare using split and independent samples.
|
From page 36... ...
36 Procedures and Guidelines for Validating Contractor Test Data testing of the contractor's results, making the SHA tests and the contractor tests independent (not from the same "samples")
|
From page 37... ...
Findings and Applications 37 designated "Fail." For the split sample sets, the Welch's t-test indicated that the SHA results and the corresponding contractor results are not statistically different; thus designated "Pass." The results can also be clearly inferred from Figures 25 and 26 where the variability of the independent samples (Figure 25) is much larger than that of the split samples (Figure 26)
|
From page 38... ...
38 Procedures and Guidelines for Validating Contractor Test Data SHA test result Contractor test result Figure 27. Illustration of the cumulative sampling technique.
|
From page 39... ...
Findings and Applications 39 However, it leaves the contractor at risk of failing validation for the duration of the project, which may not be reasonable, especially with large projects. With this method of pooling project data, sample sizes tend to grow so large that the latter tests can lose relevance.
|
From page 40... ...
40 Procedures and Guidelines for Validating Contractor Test Data In this example, the ASTM E178 procedure was applied to the data set. A comparison of the raw data indicated that the SHA data contained a potential outlier.
|
From page 41... ...
Findings and Applications 41 detected due to an abnormal condition)
|
From page 42... ...
42 Procedures and Guidelines for Validating Contractor Test Data ASTM E178 procedure (48) was applied to both SHA and contractor samples prior to conducting hypothesis testing, and no outlying observations were detected in either data set.
|
From page 43... ...
Findings and Applications 43 Figure 30. Sampling, testing, and validation process.
|
From page 44... ...
44 Procedures and Guidelines for Validating Contractor Test Data the SHA tested] using the paired t-test.
|
From page 45... ...
Findings and Applications 45 3.4 Case Study Example In this case study, data obtained from a SHA for the thickness and the compressive strength of PCC pavements were used for contractor QC data validation. The SHA specifications and the associated quality manual were used for determining the PWL values and pay adjustments.
|
From page 46... ...
46 Procedures and Guidelines for Validating Contractor Test Data level. Both tests indicated that the PCC compressive strength test results of the SHA and the corresponding contractor test results are not statistically different at this significance level; thus, "Pass" as noted in Table 14.
|
From page 47... ...
Findings and Applications 47 Thickness Pay Adjustment The PCC thickness Pay Factor, PT, is calculated as 0.01 using the following equation: P PWL T T( ) = ∗ − =0.30 100 0.27 0.01 Combined Pay Adjustment The Combined Pay Factor, P, for thickness and compressive strength is calculated as 0.04 using the following equation: ( )
|
From page 48... ...
48 Procedures and Guidelines for Validating Contractor Test Data Table 16. SHA and contractor results (original and reduced standard deviation)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.