Scales should be tested for reliability, generalizability, and validity.
Generalizability is the ability to make inferences from a sample to the population, given the scale you have selected.
Or maybe I will write a book on how to validate surveys from start to finish, sit at home, and get rich off of 10% royalties on an academic book.
Come to think of it, I’d have a better chance at becoming a statistical hero in tights that swooshes out of the sky and helps people power a Poisson regression.
The level of measurement is the type of data that is measured.