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From page 24... ... 24 A PRS must be supplemented by a sampling method that balances efficiency with contractor and agency risks. As noted in Chapter 2, accepting poor construction quality is sometimes considered. Read the entire page →
From page 25... ... Guidelines for Statistical Sampling 25 reject others. Process controls during construction (not the acceptance sampling plans) Read the entire page →
From page 26... ... 26 performance-related Specifications for pavement preservation treatments pass. There is a restriction on the number of sample failures if the lot is to be accepted (e.g., 5 samples can fail out of 50) Read the entire page →
From page 27... ... Guidelines for Statistical Sampling 27 plan n = 50, c = 5, if the lots are 10% defective, the probability of acceptance is approximately 0.62 (i.e., of 100 lots from a process that manufactures 10% defective product, 62 will be accepted and 38 will be rejected) Read the entire page →
From page 28... ... 28 performance-related Specifications for pavement preservation treatments an attributes acceptance sampling plan would require less sampling (Montgomery 2013, National Academies of Sciences, Engineering, and Medicine 2012) Read the entire page →
From page 29... ... Guidelines for Statistical Sampling 29 PWL estimates depend on sample sizes and sampling methods. Methods for estimating sample sizes and types of sampling methods are discussed next. Read the entire page →
From page 30... ... 30 performance-related Specifications for pavement preservation treatments et al. Read the entire page →
From page 31... ... Guidelines for Statistical Sampling 31 n t s E ( ) Read the entire page →
From page 32... ... 32 performance-related Specifications for pavement preservation treatments These three approaches for determining sample size for a lot estimate a high sample size to represent a lot. However, in practice, a sample size of at least five is typically used; a higher sample size is desirable, but may not be practical. Read the entire page →
From page 33... ... Guidelines for Statistical Sampling 33 Random Sampling with Replacement In this sampling method, samples of different sizes are randomly selected from any location on the lot (i.e., from one sublot or different sublots) Read the entire page →
From page 34... ... 34 performance-related Specifications for pavement preservation treatments and 20. Stratified sampling reduces bias in the selection of samples because the samples collected are highly representative of the lot. Read the entire page →
From page 35... ... Good Fair Good Bad 5% 6% 4% 6% 1% 2% 1.5% 1.8% 2.1% 3.6% 6.1% 6.6% 5.6% 4.6% 4.8% 5.0% 9.2% 9.7% 8.5% .8% Bad (a) Construction Quality 1 Fair Bad Fair Bad 2.5% 3% 3.5% 3% 1% 2% 1.5% 1.8% 1.2% 2% 1.4% 1.8% 6.2% 6.5% 7.3% 7.8% 9.2% 9.7% 8.5% 8.8% Bad (b) Read the entire page →
From page 36... ... 36 performance-related Specifications for pavement preservation treatments RQL, between AQL and RQL, and above AQL for each sampling method and size was calculated (see Table 4-1) Read the entire page →
From page 37... ... Guidelines for Statistical Sampling 37 Construction Quality between RQL and AQL The true PWL values of construction qualities 1 and 2 are 75% and 65%, respectively (see Table 4-1) Read the entire page →
From page 38... ... 38 performance-related Specifications for pavement preservation treatments Construction Quality above AQL The true PWL value of construction quality 4 is 97% (see Table 4-1) which is above the AQL of 90%. Read the entire page →
From page 39... ... Guidelines for Statistical Sampling 39 from a lot are tested and the PWL value obtained is below the RQL, the lot is rejected. However, it is possible that the three samples tested are from a sublot of a bad quality but the remaining sublots are of good quality, and therefore an incorrect decision would have been made. Read the entire page →
From page 40... ... 40 performance-related Specifications for pavement preservation treatments PWLRQL = PWL value at RQL (60%) PWLAQL = PWL value at AQL (90%) Read the entire page →
From page 41... ... Guidelines for Statistical Sampling 41 estimated PWL values and the corresponding pay adjustments might be different for different lot and sublot sizes. The effects of lot and sublot sizes on PWL estimation were evaluated using IRI as the AQC. Read the entire page →
From page 42... ... 42 performance-related Specifications for pavement preservation treatments PWL value increases (as in the cases of Montana, Nevada, and California) Read the entire page →
From page 43... ... Guidelines for Statistical Sampling 43 (a) Montana (b) Read the entire page →
From page 44... ... 44 performance-related Specifications for pavement preservation treatments for 0.1 mile) Read the entire page →
From page 45... ... Guidelines for Statistical Sampling 45 The statistical approaches used for determining sample size for a lot generally estimate a large sample size to represent a lot -- none of these approaches adequately addresses the optimum sample size. In practice, a sample size of at least five is generally used, although a larger sample size is desirable. Read the entire page →
From page 46... ... 46 performance-related Specifications for pavement preservation treatments may not be a problem if the construction variability is low (i.e., there is a uniform construction quality across the entire lot) Read the entire page →

From page 24...

... 24 A PRS must be supplemented by a sampling method that balances efficiency with contractor and agency risks. As noted in Chapter 2, accepting poor construction quality is sometimes considered.