Readability: reading-comfort levels
Here's some readability information, which I'm always interested in, and my rewrite of the original, which is a compulsion with me.
[Scholars recognize] three types of reading concepts: the independent reading level, the instructional reading level, and the frustration reading level. The independent reading level can be described as the level that an individual can read with 99% accuracy in word recognition and comprehend no less than 90% of the written material. The instructional reading level is defined as the level at which an individual can be successfully instructed, have 95% accuracy in word recognition, and understand at least 75% of the material. The frustration reading level is a level at which an individual can no longer understand reading materials and is usually marked at a word comprehension of 90% or less and a comprehension level of less than 50%. A grade level two years above the person's measured reading level is usually considered the frustration level.
Rachel Kahn, Patricia A. Zapf, & Virginia G. Cooper, Readability Of Miranda Warnings And Waivers: Implications For Evaluating Miranda Comprehension, 30 L. & Psychol. Rev. 119, 127 (2006) (citing Daniel P. Greenfield et al., Retrospective Evaluation of Miranda Reading Levels and Waiver Competency, 19 Am. J. Forensic Psychol. 75, 79-80 (2001)).
Scholars recognize three general levels of reading comfort:
Independent reading level: word recognition is 99% and comprehension is 90% or better.
Instructional reading level: (the level at which the reader can be successfully instructed) word recognition is 95% and comprehension is 75% or better.
Frustration reading level: word recognition is 90% or less and comprehension is less than 50%. At this level the reader cannot really understand the text.
A grade level two years above one's reading level is usually considered the frustration level.