Here are some possibilities:
* Mean from an established dataset: This could refer to the average value calculated from a well-known and frequently used dataset. For example, you might be talking about the "established mean" income of a certain profession, based on data from a government survey.
* Mean used as a benchmark: The term could refer to a mean value that's commonly accepted as a standard or baseline. For example, you might be talking about the "established mean" of a particular test score, used to compare individual results to the average performance.
* Mean calculated from a specific, pre-defined group: Perhaps "established mean" refers to the average calculated from a particular group that is well-defined and considered relevant to the context. For example, the "established mean" of a specific age group in a research study.
To understand what "established mean" refers to, you need more context.
Please provide more information about where you encountered this term. This could be:
* The full sentence or paragraph where it appeared
* The topic being discussed
* The field of study or research involved
With more context, I can help you understand the meaning of "established mean" and how it's being used.