Researchers routinely treat high-level ordinal scales as interval measures.

Evidence

Perhaps the most problematic and difficult to deal with are ordinal scales. We just saw that dichotomous values are often in fact ordinal. It is extremely common to see scales with three to seven different ordered levels. Quite uncommon are scales with ten or more ordinal levels. One tendency, particularly with ordinal scales with seven or more levels, is just to treat them as interval. — Gary Goertz, Social Science Concepts and Measurement, 778

Categorization

• XREF: Connects to the long-running dispute over whether Likert-scale data can legitimately be analyzed with parametric statistics.