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Readability tests

By Guðrún Unnur Gústafsdóttir

The Readability function within Quality Assurance assesses the level of your written content based on how difficult a page is to read. Although we generally recommend an overall readability score in the low/mid range of your desired test, the ideal range should be based on your target users' demography. This article is intended to inform you about the seven readability tests offered within the Readability function of Quality Assurance. 

Automated Readability Index (ARI) 

Automated Readability Index (ARI) is a readability test that works well with English and Western European languages. The test uses long words and long sentences to calculate a readability score. The score gives an indication of how difficult the page is to read. Each score can be matched to an equivalent reading ability level. ARI uses a scale based on age in full time education.  The formula for calculating the Automated Readability Index (ARI) is the following:

Characters: Number of letters and numbers

Words: Number of spaces

Sentences: Number of sentences

Best practice using ARI

A good standard to aim for is around 7th-8th grade in the US grade level system (12-14 years), which equates to a score of 9 or less. If you do not have a specific policy for reading age on your site, try and focus on the pages that  return a score of 11 and higher (10th grade +).

Note: The length of text on a web page is typically short, and the way the text is formatted can affect what is identified as content greatly. Some elements make it particularly difficult- such as lists and tables.


ARI readability scorecard

(Scores can be returned outside of the range presented on the scorecard)

Coleman-Liau 

Coleman-Liau is a readability test designed primarily for English text. The test focuses on long words and long sentences. A score can only be calculated using this test if content exceeds 100 words. The test produces an approximate representation of the US grade level needed to comprehend the text. To calculate the Coleman-Liau index, the following formula is used:


  • L is the average number of letters per 100 words
  • S is the average number of sentences per 100 words

Best practice using Coleman-Liau

A good standard to aim for is around 7th-8th grade in the US grade level system (12-14 years), which equates to a score of 8 or less. If you do not have a specific policy for reading age on your site try and focus on the pages that return a score of 10 or higher (High school sophomore +).

Note: Evaluating the readability of text written on a web page is tricky utilizing Coleman-Liau as sections of text need to be 100 words or over. This will result in only a select number of pages returning results. The way text is formatted on web pages also limits the reliability of any readability test.

Coleman-Liau readability scorecard 

(Scores can be returned outside of the range presented on the scorecard)

Flesch-Kincaid Grade Level 

Flesh-Kincaid Grade Level is a readability test designed for English text. The test has focus on polysyllabic words and long sentences. It was developed after the Reading Ease score (see below) to make it easier for parents and teachers to place reading content into appropriate reading age brackets for children. A score is returned which gives an indication of reading difficulty. This score can be related to the approximate US grade level needed to comprehend the text. When calculating Flesch-Kincaid Grade Level, the following formula is used:



Best practice

A good standard to aim for is around 7th-8th grade in the US grade level system (12-14 years). If you do not have a specific policy for reading age on your site try and focus on the pages that return a score of 10 or higher (High school sophomore +).

Note: The length of text on a web page is typically short, and the way the text is formatted can affect what is identified as content greatly. Some elements make it particularly difficult- such as lists and tables.

 Flesch-Kincaid Grade Level readability scorecard 

(Scores can be returned outside of the range presented on the scorecard)

Flesch-Kincaid Reading Ease 

Flesch-Kincaid Reading Ease is a readability test designed for English text. The test has focus on polysyllabic words and long sentences. It is widely used in US government as a way of ensuring that documents and forms are understandable for the "average" American. Results are measured on a scale of 0-100, where 0 is very complicated to read and 100 is very easy to read. This score can be related to the approximate US grade level needed to comprehend the text. When calculating Flesch-Kincaid Reading Ease, the following formula is used:

Best practice

A good standard to aim for is around 7th-8th grade in the US grade level system (12-14 years), which equates to the 60-70 range or higher. If you do not have a specific policy for reading age on your site try and focus on the pages that return a score of 60 or lower (10th grade +).

Note: The length of text on a web page is typically short, and the way the text is formatted can affect what is identified as content greatly. Some elements make it particularly difficult - such as lists and tables.

 Flesch-Kincaid Reading Ease readability scorecard

 (Scores can be returned outside of the range presented on the scorecard)

Gunning Fog 

Gunning Fog is a readability test just for English texts. The test focuses on complex words (polysyllabic words) and long sentences. A score can only be calculated using this test if the content of the page is over 100 words, making it a hard test to apply to web pages. The test produces an approximate representation of the US grade level needed to comprehend the text. When calculating Gunning Fog, the following formula is used:


  1. Select a passage (such as one or more full paragraphs) of around 100 words. Do not omit any sentences.
  2. Determine the average sentence length. (Divide the number of words by the number of sentences.).
  3. Count the "complex" words: those with three or more syllables. Do not include proper nouns, familiar jargon, or compound words. Do not include common suffixes (such as -es, -ed, or -ing) as a syllable.
  4. Add the average sentence length and the percentage of complex words.
  5. Multiply the result by 0.4.

Best practice

A good standard to aim for is around 7th-8th grade in the US grade level system (12-14 years), which equates to a score of 8 or less. If you do not have a specific policy for reading age on your site try and focus on the pages that return a score of 10 or higher (High school sophomore +).

Note: Evaluating the readability of text written on a web page is tricky utilizing Gunning Fog as sections of text need to be around 100 words. This will result in only a select number of pages returning results. The way text is formatted on web pages also limits the reliability of any readability test.

Gunning Fog readability scorecard 

(Scores can be returned outside of the range presented on the scorecard)

LIX 

LIX is a readability test that performs well on most of the Western European languages. The test focuses on total words, number of sentences and number of long words (more than 6 characters). A score is returned which gives an indication of reading ease. When calculating LIX, the following formula is used:

 , where:

  • A is the number of words
  • B is the number of periods (defined by period, colon or capital first letter), and
  • C is the number of long words (more than 6 letters)

Best practice

A good standard to aim for is a score that relates to the text being understandable for practiced readers, which equates to the range 20-30 or less. If you do not have a specific policy for reading age on your site try and focus on the pages that return a score of 40 or higher.

Note: The length of text on a web page is typically short, and the way the text is formatted can affect what is identified as content greatly. Some elements make it particularly difficult - such as lists and tables.

LIX readability scorecard

(Scores can be returned outside of the range presented on the scorecard)

SMOG ‌‌

SMOG is a readability test just for English texts. The test focuses primarily on polysyllabic words. A score can only be calculated using this test if the content of the page has at least 30 sentences, making it a hard test to apply to all web pages. The test produces an approximate representation of the US grade level needed to comprehend the text. When calculating SMOG, the following formula is used:

1. Count the number if sentences (at least 30).

2. In those sentences, count the polysyllables (words of 3 or more syllables).

3. Calculate using the above formula.

Best practice

A good standard to aim for is around 7th-8th grade in the US grade level system (12-14 years), which equates to a score of 8 or less. If you do not have a specific policy for reading age on your site try and focus on the pages that return a score of 10 or higher (High school sophomore +).

Note: Evaluating the readability of text written on a web page is tricky utilizing SMOG as it requires 30 sentences to be present in the content of a page. This will result in only a select number of pages returning results. The way text is formatted on web pages also limits the reliability of any readability test.

SMOG readability scorecard

 (Scores can be returned outside of the range presented on the scorecard)

 

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