Readability

What does readability mean?

A readability score is a measure of the relative accessibility of written text usually reported as a numerical value keyed either to a grade level or to a point scale. It is usually calculated using a mathematical formula that considers features of a given text, such as word length, incidences of multi-syllabic words, and sentence length.

Resources are measured for readability on a point scale of 1 to 5, where 1 corresponds to low reading difficulty and 5 corresponds to high reading difficulty. netTrekker then prominently displays a score for each resource, even providing quick refinement options that allow you to click to content that meets your desired readability level.

Example of a Readability score

The relationship between grade levels and the readability scores is as follows:

Readability Score
Grade-Level Readability
Equivalent
1 – 3
4 – 6
7 – 8
9 – 10
11 – 13
See Below*

To refine your Search Result to display specific chosen readability levels, simply click on one or more of the active boxes in the Readability menu in Refine Search. If a level is grayed out, there are no items in your search result for that readability level. To return to your original results, just click on the Reset link at the bottom of Narrow Search.

Example of Readability Menu in Refine Search

What is the Readability Score based on?

Readability Scores in netTrekker
The netTrekker readability score is a composite, an average of the scores generated by four long-standing readability formulas and the Lexile® Framework for Reading, these are the Automated Readability Index (ARI), Flesch-Kincaid Index, Gunning Fog Index (GFI), and McLaughlin SMOG Readability Formula. The documentation for the style and diction program used by netTrekker to generate readability scores can be found at http://manpages.ubuntu.com/manpages/precise/man1/style.1.html

Automated Readability Index (ARI)

Results filtered using the ARI readability measure are grade-level equivalents. The ARI formula takes into account the number of words in a sentence, as well as the number of letters in each word.

Formula:
ARI = (4.71 x AVL) + (0.5 x AVW) – 21.43
    where
AVL = the average number of letters per word
AVW = the average number of words in sentences
Coleman-Liau Grade Level

Results filtered through the Coleman-Liau measure are grade-level equivalents. The Coleman-Liau Grade Level takes into account the number of sentences, as well as the number of letters in each word.

Formula:
Coleman-Liau = (5.89 x AVL) – (0.3 x ADJS) – 15.8
    where
AVL = the average number of letters per word
ADJS = (100 x number of sentences)/number of words in the composition
Flesch-Kincaid Index

The Flesch-Kincaid Index is a modified version of the Flesch Reading Ease scale that converts the Reading Ease score to a grade-level equivalent. Results filtered using the Flesch-Kincaid Index readability measure are grade-level equivalents.

Formula:
Flesch-Kincaid = (AVSY*11.8) + (AVW*.39) – 15.59
    where
AVSY = the average number of syllables per word
AVW = the average number of words in sentences
Flesch Reading Ease

Flesch Reading Ease measures reading difficulty on a 100-point scale; the higher the score, the easier a site is to read. Flesch Reading Ease takes into account the number of syllables per word and the number of words per sentence.

Formula:
Flesch Reading Ease = 206.835 – (AVSY x 84.6) – (AVW  x 1.015)
    where
AVSY = the average number of syllables per word
AVW = the average number of words in sentences

Gunning Fog Index (GFI)

The Gunning Fog Index (GFI) provides a measure of reading difficulty based on school grade levels. It calculates a grade-level equivalent score by counting words of three or more syllables, number of sentences, and average number of words in sentences.

Formula:
Fog Index = 0.4 x words/sentence + 100 x [(words >= 3 syllables)/words]
Lexile® Framework for Reading

Lexile measures are based on two well-established indicators of how difficult a text is to comprehend: semantic difficulty (vocabulary-based familiarity of words and phrases) and syntactic complexity (sentence length). Text passages are fed into a proprietary analyzer to determine Lexile scores. A Lexile score can then be translated into a grade-level equivalent. Because of the particular rules that the Lexile analyzer uses to determine if a site or resource is appropriate for analysis, the percentage of sites that are given Lexile scores is approximately 50 percent.

The relationship between grade level and Lexile scores from MetaMetrics, Inc. is given here:

The relationship between grade level and Lexile scores:
Grade 1 200L – 350L
Grade 2 350L – 500L
Grade 3 500L – 750L
Grade 4 620L – 910L
Grade 5 730L – 960L
Grade 6 800L – 1030L
Grade 7 880L – 1090L
Grade 8 910L – 1140L
Grade 9 1030L – 1160L
Grade 10 1080L – 1210L
Grade 11 1130L – 1260L
Grade 12 1180L – 1300L

To learn more about the Lexile® Framework for Reading, please click here.

To read more about the alignment of Lexile scores to other instructional reading programs, such as Fountas and Pinnell, click here.

Lix
Lix scores usually range from 20 (very easy to read) to 60 (very difficult to read).
Lix Formula:

Lix = words/sentences + (words > 6 characters)/words
Lix-Grade
Results filtered using the Lix-Grade readability measure are grade-level equivalents of Lix scale scores mapped as follows:
Lix-Grade Formula:

McLaughlin SMOG Readability Formula

Results filtered using the SMOG readability measure are grade-level equivalents.

McLaughlin SMOG Readability Formula:
SMOG = square root of [(words >= 3 syllables) x (sentences > 30 words)] + 3
N/A Readability Scores

Occasionally netTrekker is unable to calculate a readability score for a website. Learn more here.

Viewing All Readability Measures

To view all readability measures for a website or resource, simply click on the View Content Details link. This button is displayed on every search result.

Example of using the View Content Details link

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