Readability formulas measure surface level text features.

Quantitive measures are the first step in determining text readability for a student.

When I saw the bug, I screamed out of fright.
When I saw the Bug, I was reminded of my first car.
When I saw the bug, I realized the spies had located me.

Readability can be seductive and misleading because it measures frustration, instruction and independence only.
Doesn't measure content, quality of text, reader interest, and goal setting.