Assessment and Interlaboratory Comparisons Stephen Nightingale, NIST May 27, 2009
Introduction to Assessment – The accreditor needs to assess test laboratories and their staff for: • Technical competence, and • Quality procedures. – This includes assessment of laboratory staff competence to conduct testing. – Assessment of the lab’s test method validation records, • Staff understanding of validation and traceability. • Staff knowledge of protocol domains. – Interlaboratory comparisons: • To determine that every lab gets the same results with the same test items.
Technical Assessment – The technical assessment: • Occurs before accreditation and about every two years after. • Examines the methods in a test laboratory’s scope. • Makes sure that test labs have access to the test specifications, and that qualified staff are familiar with them. • Determines test lab staff familiarity with the traceability chain, • Determines test lab staff knowledge of applicable protocol domains. • Assesses test lab staff competence with the test methods.
Validation – Validation is a procedure to determine that the use of the test specifications with the designated test method yields test interpretations faithful to the RFCs. – It is conducted in-house by the test laboratory staff on establishing a new test method. – It is conducted for each test method in the lab’s Scope of Accreditation.
Validation – Validation of the test method against the test specifications is the responsibility of the test laboratory • Qualified test staff for each functional area need to do this. • Validation is a background activity not directly part of the testing chain. • It is conducted once per major test suite release. • It is NOT a ‘sampling’ activity. • The assessor will examine validation records for technical completeness.
Validation for Conformance, Interoperability, Network Protection – Conformance testing is most automatable. • Validation entails running every test and checking that all packets generated by the test tool are syntactically correct and in the correct sequence. – Interoperability testing is procedural. • Validating the tests involves making sure that the prescribed actions are correct according to the RFCs. – Network protection testing is procedural. • It involves packet exchange and operator interface and environment testing. • Validation entails making sure the tests are correct according to the network protection specification.
Interlaboratory Comparisons – The objective is to make sure that testing done in test laboratories yields identical results for the same items. – This is usually conducted by the accreditor, but if there are multiple accreditors, interlaboratory comparisons should be conducted by a single independent organization. – Interlaboratory comparisons should be done by sending sample test items to every test lab, and looking for identical results.
Summary • Assessment tests a laboratory’s competence with protocols and test methods. • Validation makes sure the tests and procedures yield results correct according to the RFCs and protocol specifications. • Interlaboratory comparison tests every laboratory’s ability to produce the same results.
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