Sociolinguistics 10, Exercise 3: "a study proves people from region X speak badly"

Any four of these questions from the chapter's critical-reading list:
1. How was the speech collected, and could the observer's paradox have
   changed it?
2. Does the claim describe a group, or is it being applied to every
   individual?
3. Is "proves" or "badly" the source's own strong word, and what was
   measured? "Badly" is a judgment of prestige, not a linguistic measurement
   (Chapters 2, 5 and 8: the standard is a social choice, and beliefs in its
   superiority are "firmly rooted in social perceptions").
4. Is the figure an estimate with a wide range?

A fifth point from Chapter 8: findings about perceived intelligence or skill
are perceptions, not a measurement of ability.