Final answer:
The marketing researcher should ask if the data is internally consistent in light of known data sources when establishing the reliability of secondary data sources in the international arena.
Step-by-step explanation:
The marketing researcher should ask the following question when establishing the reliability of secondary data sources:
- Are the data internally consistent in light of known data sources?
This question is important because it ensures that the secondary data is consistent and reliable with other sources of data. By comparing the secondary data with known data sources, the researcher can determine if there are any inconsistencies or discrepancies that may affect the reliability of the data.