2.74, unhelpful sentence

[michaeladamkatz]

This is a matter of taste, but I really dislike statements like "Selection bias is a pretty broad term." What does "pretty broad" mean? How does this sentence in any way help me understand what selection bias is? The example that follows helps me understand, but it would be better if this introductory sentence said what selection bias is in general, instead of just saying it's "broad."