List of readability tests facts for kids
This article is about special formulas that help us guess how hard a piece of writing will be to read and understand. These are often called "readability formulas."
Contents
What Makes Text Hard to Read?
Have you ever read something that was really hard to understand? Or something super easy? Readability formulas are tools that try to predict how difficult a text is.
Scientists have found two main things that make reading harder or easier:
- Hard words: This is about the words themselves. Rare words are usually harder to understand than common ones. Often, longer words are also harder.
- Hard sentences: This is about how sentences are put together. Long, complicated sentences are tougher to read than short, simple sentences.
Some formulas only look at how hard the words are. Others also look at how long or complex the sentences are.
How Do We Know if Formulas Work?
We can check if these formulas work well by comparing them to each other. More importantly, we check how well they predict how easy a text is for real readers.
One way to do this is to use special test passages that are already known to be easy or hard. The best formulas are about 70% accurate at predicting difficulty. Many tests have shown that these formulas usually match how well people understand a text. They also match the reading levels chosen by experienced teachers. For example, one study found that when a farm magazine was made easier to read, many more people started reading it!
Formulas Using One Main Idea
SMOG
The SMOG formula uses one main idea to guess how hard a text is. G. Harry McLaughlin created it in 1969 to be super simple to use. Like another formula called Gunning-Fog, SMOG looks for words with three or more syllables. These are called "polysyllabic" words and are seen as harder.
The original SMOG formula was for texts with 30 sentences. It looks like this:
You can also change it to work with any number of sentences:
McLaughlin also made a simpler version you can do in your head:
- Count words with three or more syllables (don't count names) in 30 sentences.
- Find the square root of that number (or the closest perfect square).
- Add 3 to get the estimated SMOG grade.
Formulas Using Two Main Ideas
The Dale–Chall Formula
Edgar Dale, a professor, and Jeanne S. Chall created this formula in 1948. Dale had made a list of 3,000 easy words that most fourth-grade students understood. This list is a key part of their formula.
To use this formula:
- Pick several 100-word parts from the text.
- Figure out the average sentence length (words divided by sentences).
- Find the percentage of words that are NOT on Dale's list of 3,000 easy words. These are the "difficult words."
- Use this equation:
Raw Score = 0.1579PDW + 0.0496ASL + 3.6365
Where:
- Raw Score = The reading grade level.
- PDW = Percentage of Difficult Words.
- ASL = Average Sentence Length.
Finally, use this chart to get the final grade level:
| Raw Score | Final Score |
|---|---|
| 4.9 and below | Grade 4 and below |
| 5.0 to 5.9 | Grades 5–6 |
| 6.0 to 6.9 | Grades 7–8 |
| 7.0 to 7.9 | Grades 9–10 |
| 8.0 to 8.9 | Grades 11–12 |
| 9.0 to 9.9 | Grades 13–15 (college) |
| 10 and above | Grades 16 and above |
In 1995, Dale and Chall updated their formula with a new word list.
Flesch Reading-Ease Score
The formula for the Flesch reading-ease score is:
Higher scores mean the text is easier to read. Here's how to understand the scores:
| Score | Notes |
|---|---|
| 90.0–100.0 | Easily understood by an average 11-year-old student |
| 60.0–70.0 | Easily understood by 13- to 15-year-old students |
| 0.0–30.0 | Best understood by university graduates |
The United States Department of Defense uses this test to check how readable its documents are. In Florida, life insurance policies must have a Flesch reading ease score of 45 or higher. Many popular word processing programs like Microsoft Word also include this tool.
Gunning Fog
The Gunning Fog index, also called the Fog index, was created by Robert Gunning. It first appeared in his 1952 book The Technique of Clear Writing. It became popular because it's easy to calculate.
Some people have criticized this formula because it mainly focuses on sentence length. They argue that texts made with this formula might use shorter sentences but still have difficult words. However, the job of readability tests is to predict how hard a text is, not to tell you how to write better. Sentence length is a good sign of how complex the sentences are.
The formula is:
![\mbox{Gunning Fog grade} = 0.4 \times \left [ \frac{ \mbox{words} }{ \mbox{sentences} } + \left ( 100 \times \frac{ \mbox{hard words} }{\mbox{words}} \right ) \right ]](/images/math/6/0/8/6086d4db623b0933613dff726b2b5eed.png)
Where:
- words is the total number of words.
- sentences is the total number of sentences.
- hard words are words with three or more syllables (not counting names or compound words).
Spache
The Spache method compares words in a text to a list of words that are common in everyday writing. Words not on this list are called unfamiliar. The formula also counts the number of words per sentence. These numbers are put into a formula to give a reading age. Someone of that age should be able to read the text. It's made for texts written for children in elementary school (grades 1 to 7).
The formula is:
In 1974, Spache updated his formula to:
Coleman-Liau Index
The Coleman-Liau Index calculates readability in two steps. The first step finds an "Estimated Close Percentage," and the second step calculates the actual grade level.
The main formulas are:
There's also a simpler, but less accurate, version:
Automated Readability Index
The Automated Readability Index was created to quickly figure out readability using early electric typewriters.
The formula is:
