Frequently Asked Questions - Proficiency Samples
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How do I get started?
What are the requirements for participating laboratories?
To participate, a laboratory must be equipped to perform some or all of the standard AASHTO or ASTM tests on soils, aggregates, asphalt binder,
asphalt emulsion, or hot mix asphalt.
What tests am I required to perform on a sample?
A non-accredited laboratory may perform any (or all) of the AASHTO or ASTM tests on a sample pair. Accredited laboratories must perform all offered test methods within the scope of their accreditation (i.e. every accredited test).
How have labs performed in the past?
How can I submit my results?
You may submit your results online (you must be logged in to do this) or you may fax or mail us your results.
How do I save an electronic copy of my ratings sheet?
Sign in and access your ratings sheet on the website. To save the ratings page as a file on your computer click on "File" and "Save As" and designate the location
to which you want the file saved.
How and when do I respond to low ratings on a proficiency sample?
Within 60 days of the date on the final report, an accredited laboratory receiving a +/- 2, +/- 1, or zero rating must investigate the root cause of the low ratings. A standard Proficiency Sample Corrective Action Report Form is available. Keep a copy
for your own records, but these records are not required to be submitted to AMRL.
What do the ratings for “repeatability (within-lab)” mean?
Repeatability is an estimate of the variation in results that you might expect if you repeated the same test over and over in your laboratory. The within-lab
rating is based on the difference between the two individual lab results, but also subtracts out any actual differences between the two sample materials (the manner
is similar to what we have always done when computing single operator statistics for the compilation of statistics).
An “individual within-lab value" is determined for each lab as follows:
- Individual Within-Lab Value = [(Yi-Xi)-(Yavg-Xavg)]/(square root of 2)
- The standard deviation of those values is the repeatability (or within-lab) standard deviation, 1S.
- The "Within-Lab Ratings" are determined using the "Individual Within-Lab Values" and the "Within-Lab Standard Deviation, 1S" to determine within-lab
Z-Scores. Then, the same rating scheme is used as for the individual samples.
Do laboratories that receive low ratings for “repeatability (within-lab)” need to respond to AMRL?
No. You should examine why your within-lab results may not be as consistent in your laboratory as in other laboratories, but you are not required to submit a
response to AMRL at this time.