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Table 1 Instruments and calculations used to assess readability

From: Readability and quality assessment of internet-based patient education materials related to nasal septoplasty

Assessment Scale Formula
FRE FRE = 206.835 − (84.6 × \( \frac{syllables}{words} \)) − (1.015 × \( \frac{words}{sentences} \))
FKG FKG = (11.8 × \( \frac{syllables}{words} \)) + (0.39 × \( \frac{words}{sentences} \)) − 15.59
GFI GFI = 0.4 × [(\( \frac{words}{sentences} \)) + (\( \frac{\sigma }{words} \) × 100)]
σ=number of words with greater than or equal to 3 syllables
CLI CLI = (0.0588 × γ) − (0.296 × ω) − 15.8
γ=average number of letters per 100 words
ω=average number of sentences per 100 words
SMOG SMOG
= 1.0430 × \( \sqrt{\sigma \times \frac{30}{number\ of\ sentences}} \) +  3.1291
σ=number of words greater than or equal to 3 syllables
ARI ARI = (4.17× \( \frac{characters}{words} \)) + (0.5 × \( \frac{words}{sentences} \)) − 21.43
  1. FRE Flesch Reading Ease, FKG Flesch Kincaid Grade Level, GFI Gunning-Fog Index, CLI Coleman-Liau Index, SMOG Simple Measure of Gobbledygook Index, ARI Automated Readability Index