Review of F and t Test Results 2000 Through 2004

Details

• Creators:
  Chavez, Eric
• Corporate Creators:
  Colorado. Department of Transportation
• Corporate Contributors:
  United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  • Analysis of variance
  • Concrete pavements
  • Contractors
  • Flexural strength
  • Hot mix asphalt
  • Incentives
  • Payment
  • Portland cement concrete
  • Quality assurance
  • Quality control
  More +
• Publication/ Report Number:
  CDOT-DTD-R-2005-17
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Colorado
• Edition:
  Final Report
• Corporate Publisher:
  Colorado. Department of Transportation
• Abstract:
  The Colorado Department of Transportation (CDOT) uses the F test and t test to determine if two sets of test data are from the same population. The comparison is usually between the Contractor's quality control tests and the Department's verification tests. The F test and t test are calculated in accordance with standard statistical procedures to make the comparisons. The F test analyzes the differences in the standard deviations of the data sets. The t test analyzes differences in the means of the data sets. Starting in 1988 the first projects were awarded under pilot specifications which contained the requirement for F and t test analysis. Analysis was conducted between the Contractor's and the Department's flexural strength tests on these first projects. The specification was released as a standard specification on February 11, 2000 titled: Revision of Sections 105, 106, and 412, Quality of Portland Cement Concrete Pavement (Alternative Strength Criteria). This report analyzes the F and t test results from 2000 through 2004. Eight of the projects evaluated in this report contain the alternative strength specification. Two projects included in this report contained modified specifications: ten year warranty PCCP & ten year warranty HMA. Analysis on ten projects is included in this report. On two of the projects the F and t test analysis was designated as being for informational purposes only by the engineer. Regardless of the outcome of the F and t tests, the Contractor's tests results were used on one of these projects. CDOT's test results were used on the other. On both of these projects the F and t test passed on all processes. Of the ten projects evaluated five passed both tests on all processes. Three projects had at least one failing test in the t test. Two projects failed both tests on all processes. Twenty-two processes were established for the material being evaluated. The F tests passed in all but two of the processes. The variation of the data between the Contractor and the Department was within allowable differences 91% of the time. The t test failed on 7 of the processes, 32% of the time. There was a consistent difference between the two sets of test results on these processes. CDOT's test results were used instead of the Contractor's for the calculation of I/DPs on four processes because of failing F and t test results.
• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/93183/dot_93183_DS1.pdf
• File Type:
  [PDF - 673.99 KB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:26347630b068d3cd404803c855c555e4505c9bd69af2c8d38f9e733fa7fd4ffde07c01c4a6394e55e1ed0dc4a36d25932cd075749238d2cef6cca9e7892da3ff