Table 1.

Assessment scales used for consent form readability59, 60, 61

Assessment scale	Formula	Output
Flesch Reading Ease Formula	= 206.835 – (1.015 × ASL) – (84.6 × ASW)	Score form 0–100 90–100 = 5th grade reading level 60–70 = 8th and 9th grade reading level 0–30 = college graduate reading level
Flesch–Kincaid Grade Level	= (0.39 × ASL) + (11.8 × ASW) – 15.59	Average student of the grade can read the text.
Fog Scale	= 0.4 (ASL + PHW)	5 = readable 10 = hard 20 = very difficult
SMOG Index	= 1.043 × √ (C × (30/S)) + 3.1291	Average student of the grade can read the text
Coleman–Liau Index	= 0.0588L – 0.00296S – 15.8	Average student of the grade can read the text
Automated Readability Index	= 4.71 (characters/words) + 0.5 (words/sentences) – 21.43	Average student of the grade can read the text
Linsear Write Formula	= (R + 3C)/S Then: If >20, divide by 2 If ≤20, subtract 2, and then divide by 2	Average student of the grade can read the text

ASL = average sentence length (i.e., the number of words divided by the number of sentences [S]); ASW = average number of syllables per word (i.e., the number of syllables divided by the number of words); PHW = percentage of hard words (i.e., the number of 3+ syllable words [C] divided by the number or words in the sample passage); R = the number of words ≤2 syllables; L = the average number of letters per 100 words; average student of the grade can read the text = US school grade level (e.g., 7.4 = 7th grade).