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The Raygor Readability Estimate

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A readability score, or index, is an estimation of how difficult a text is to read. If you aren't familiar with what a readability index is and what it measures, we invite you to read our treatment of the topic here.
The Raygor readability score is another visual assessment of grade-level similar to the better known Fry Readability Formula. The method, developed by Alton Raygor in 1977, is to take three 100-word samples, with one chosen from the beginning, middle, and end of the text. Count the number of sentences (with incomplete sentences counting as half) and count the number of words having six or more letters. We then plot the number of words having 6 or more characters per 100 words on the horizontal axis (x-axis) and the number of sentences per 100 words on the vertical axis (y-axis) on the Raygor graph seen below. The region this point lies in is an estimation of the grade level of a text.
As in the case of the Edward Fry's Readability Formula, computers weren't widely available to the public at the time Raygor developed the above method. So his method was fast, accessible, and could be calculated quickly on paper so that educators or anyone else could objectively estimate the reading level of a text. Modern computing, however, allows us to not only compute the above index for several 100-word samples, but to perform the above task for the entire text almost instantaneously. This website calculates the Raygor Readability Score for the entire text.

An Example

We shall estimate the grade level of the text "The Happy Prince," by Oscar Wilde. Below is the Raygor Readability graph for the entire text (red dot). The dot falls in the region labelled "6," which means the grade level of the text is about sixth grade.
Raygor Readability Formula
The engaged reader should run the same test on our homepage.

Other Features on this Website

On this website, provided your text contains more than 600 words, you may calculate the Raygor Readability Score for as many random 500-word samples of your text as you like. Below is the same graph as above with several randomly chosen 500-word samples. The darkness of the dot represents where in the text the sample was taken from. Lighter dots indicate that the a 500-word sample closer to the beginning of the text, whereas darker dots indicate a sample closer to the end.
Raygor Readability Formula
You may also plot every 500-word sample from the beginning to the end of the text as seen below.
Raygor Readability Formula
We can see from the above graph that the grade level estimations of most 500 word samples of "The Happy Prince" lie mostly between 5th and 7th grade with the average (red dot) lying in the 6th grade region.

Limitations

For texts with exceedingly long words or sentences, the Raygor Readability Formula is inconclusive. That is, when the dot falls into the pinkish/purplish regions labelled either "long words" or "long sentences," a grade level cannot be determined. For example, if we feed the following nonsense text into the formula,
Dashjkldsfhjlksadfhjlkdf daseuioepruoad dsfjklasdfnjklsadf and dsajgkquzndjwisnw!
we get an an inconclusive result as seen below.
Raygor Readability Formula

Conclusions

Both Alton Raygor and Edward Fry set out to make the readability of a text a reasonably easy thing to objectively estimate. And likewise, at Analyze My Writing, we try give you tools which make estimating the reading level of a text a little easier.
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Links and References

DuBay, W. H. 2006. Smart language: Readers, Readability, and the Grading of Text. Costa Mesa:Impact Information.
Fry, E. B. 1968. A readability formula that saves time. Journal of reading 11:513–516.
Article on this Website: What is a Readability Index?.
Article on this Website: The Fry Readability Formula.
Wikipedia Article on Fry Readability Formula.
Wikipedia Article on Raygor Readability Estimate.
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