A Nuclear Industry Code of Practice
Principles, Processes and Practices for use by the Nuclear Industry
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- Clearance and Exemption Principles, Processes and Practices for Use by the Nuclear Industry - August 2006 (file size: 1.76MB, .pdf format)
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Stats Statement on Error in COP
Significant problems have been identified with the content of Ch 7 and the CEWG is working on a complete revision as a priority activity.
In particular, the equations for Nv, the number of samples required, in section 7.2.2.6 are incorrect for both class 1 and class 2 materials. As an alternative, for class 1 the CEWG recommends the use of an equation contained in the appendix to “Guidance on Systematic Planning Using the Data Quality Objectives Process”, document reference EPA QA/G-4, which can be found at http://www.epa.gov/quality/qs-docs/g4-final.pdf. There is currently no recommended alternative equation for class 2 materials.
Within the COP a variety of symbols is used for the mean and standard deviation; this will be rationalised as part of the revision process.
In addition, questions have been raised on the validity of the equations for the Wilcoxon signed rank test (W<Wcrit) in appendix 7.7 and the Student’s t test (t<tcrit) in Appendix 7.8. Corrected text is provided in the following attachment.
On the basis of the stated the Null hypothesis H0 being that the material is radioactive then Appendices 7.7 and 7.8 should read as follows:
Appendix 7.8, Stage 5
If t>tcrit then the material is exempt (ie the null hypothesis is rejected).
Otherwise, t<tcrit and the material is not exempt (ie the null hypothesis is accepted)
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