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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-RD-03-041
Figure 68 in page 111 shows the results of one-sided t-tests with 95 percent confidence level on whether the absolute differences between as-constructed (elevation-measured) and as-designed thicknesses are below, within, or above the tolerance level (TV) of 12.7 mm. A chart is presented for the percentage distribution of the absolute differences for six material types including DGAB, DGATB, LC, PATB, PCC, and SB from the corresponding target thickness listed in Table 55 in page 109. The percentage is determined by the number of sections with the absolute differences below, within, or above the tolerance level (TV) of 12.7 mm divided by the total number of sections for the corresponding target thickness. The horizontal axis of the chart is the corresponding target thicknesses for each of the six material types. The vertical axis is the percentage of the absolute differences that are below, within, or above the TV of 12.7 mm, which are displayed as a vertical bar of 100 percent in total, consisting of black (below the TV of 12.7 mm), blank (within the TV of 12.7 mm), and gray (above the TV of 12.7 mm) percentages. On average for the six material types, about 10.3 percent of absolute differences are below the TV of 12.7 mm; about 76.8 percent of the absolute differences are within the TV of 12.7 mm; and about 12.8 percent of the absolute differences are above the TV of 12.7 mm.