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35 Table 42. Flow numbers for chart showing these results. Figure 24 includes the mean flow unconfined tests. number obtained with each device, and 95 percent confidence intervals based on the pooled standard deviation from the Replicate ITC IPC MDTS 1 1027 917 760 three devices. The pooled coefficient of variation in these tests 2 891 906 961 is 10.8 percent, which is much lower than the value of 35 per- 3 918 893 1164 cent obtained for this same mixture in Phase II of the proj- 4 1093 978 1106 Average 982 924 968 ect (11). The lower variability reported here is the result of the Standard Deviation 94.4 37.6 180.0 improved flow number algorithm developed at ASU. SSW 26723 4249 97233 3.4 Repeatability flow point, the coefficient of variation in the unconfined test is less than 10 percent. At high strain levels, the coefficient of vari- The data from the equipment effects experiment can be ation is similar for confined and unconfined tests. used to make initial estimates of the repeatability of the dy- An analysis of variance was also conducted on flow num- namic modulus and flow number tests. These estimates of re- bers obtained from unconfined repeated load permanent de- peatability can be useful in early evaluations of the equipment formation tests. The flow number of each of these tests was and in the planning of an interlaboratory study where formal computed using the improved algorithm developed at the statements of both the repeatability, within laboratory preci- Arizona State University (ASU) for detecting the flow num- sion, and reproducibility, between laboratory precision, of ber with the Franken model (14). The flow number data are the tests are developed. summarized in Table 42. Table 43 presents the results of the The term "difference two standard deviation limit" or d2s analysis of variance for the flow numbers. The conclusion is used to define the repeatability of a test method. For tests from this analysis is that the flow number is not significantly conducted within a laboratory, the difference in two meas- affected by the type of equipment. Figure 24 presents a bar urements on the same material should not exceed the d2s Table 43. Analysis of variance for flow number. Source of Degree of Sum of Mean F Statistic Conclusion Variation Freedom Squares Squares Between 2 12273 6136 0.43< Fcr =4.64 Not a significant Within 9 128204 14245 equipment effect Total 11 MDTS IPC ITC 0 200 400 600 800 1000 1200 1400 Flow Number Figure 24. Bar chart for flow number.