The information comes from a variety of sources within the medical record, such as clinical notes, laboratory and radiology results, and operation notes. Assignment The assignment phase has two parts: finding the appropriate code(s) from the classification for the abstraction; and entering the code into the system being used to collect the coded data. Review Reviewing the code set produced from the assignment phase is very important. Clinical coder must ask themselves, "does this code set fairly represent what happened to this patient in this health encounter at this facility?" By doing this, clinical coders are checking that they have covered everything that they must, but not used extraneous codes. For health encounters that are funded through a case mix mechanism, the clinical coder will also review the diagnosis-related group (DRG) to ensure that it does fairly represent the health encounter. Competency levels Clinical coders may have different competency levels depending on the specific tasks and employment setting. Entry-level / trainee coder An entry level coder has completed (or nearly completed) an introductory training program in using clinical classifications. Depending on the country; this program may be in the form of a certificate, or even a degree; which has to be earned before the trainee is allowed to start coding. All trainee coders will have some form of continuous, on-the-job training; often being overseen by a more senior coder. Intermediate level coder An intermediate level coder has acquired the skills necessary to code many cases independently. Coders at this level are also able to code cases with incomplete information. They have a good understanding of anatomy and physiology along with disease processes. Intermediate level coders have their work audited periodically by an Advanced coder. Advanced level / senior coder Advanced level and senior coders are authorized to code all cases including the most complex. Advanced coders will usually be credentialed and will have several years of experience. An advanced coder is also able to train entry-level coders. Nosologist A nosologist understands how the classification is underpinned. Nosologists consult nationally and internationally to resolve issues in the classification and are viewed as experts who can not only code, but design and deliver education, assist in the development of the classification and the rules for using it. Nosologists are usually expert in more than one classification, including morbidity, mortality and casemix. In some countries the term "nosologist" is used as a catch-all