5.3.2 Aggregation

In order to obtain a continuum ranging from literate to oral style, the two features word and sentence length must be aggregated into a so called Readability Index, which is calculated by applying the Flesch Reading Ease Test to the texts mentioned above. A high Readability Index is assumed to be an indicator of a more oral characterization of a text, as it features mostly short word and sentence constructions and vice versa.

The Flesch Reading Ease Test is one of the two Flesch - Kincaid readability tests, the second being the Flesch - Kincaid Grade Level Test. Both tests correlate inversely, meaning that a text with a high score on the Reading Ease Test should have a low score on the Grade Level test and vice versa. This is due to the fact that although both tests use the same measures (word length and sentence length), they have different weighting factors. While the Reading Ease Test indicates a text’s Readability Index by rating tests on a 100-point scale, the Flesch-Kincaid Grade Level Test produces a number which corresponds with a grade level, thus indicating a text’s grade level score (for a text to be appropriate for an 8th grader it would, for instance, have to have a grade level score of somewhere around 8).

Both systems were developed by J. Peter Kincaid and Rudolph Flesch and were originally devised for military purposes such as assessing the difficulty of technical manuals, but since then have been applied in various ways. Today, they are frequently used in the field of education, journalism, research, health care, law, insurance, and industry. Also, Microsoft Word offers an application which allows the user to test his or her document’s readability level by prompting Word to display the readability score according to the Flesch - Kincaid readability tests. For more information on how to test your document’s readability with Microsoft Word go to http://office.microsoft.com/en-us/word-help/test-your-document-s-readability-HP010148506.aspx

For this case study, it will, however, suffice to apply only one of the two tests as both systems essentially measure the same thing. Therefore, we will direct our interest exclusively towards the Flesch Reading Ease Test and its underlying formula:

206.835 – (1.015 x ASL) – (84.6 x ASW)

ASL refers to the average sentence length which is produced by dividing the number of words by the number of sentences.

ASW refers to the average number of syllables per word which is produced by dividing the number of syllables by the number of words.

In this regard, it is important to keep in mind that this formula only measures the surface characteristics of a test, meaning that qualitative factors such as vocabulary difficulty, composition, sentence structure, concreteness and abstractness, obscurity and incoherence, which may also have a notable impact on the readability and the communicative function of a text are not taken into account. It should also be noted that the usefulness of readability tests is far from being undisputed. Although, it is a fact that these tests are increasingly being applied in various fields and areas, there are still those who are opposed to their use as they believe them to be inaccurate. The International Reading Association and the U.S. National Council of Teachers of English are, for instance, advising members against uncritical use of readability tests to assess educational materials.

Keeping these concerns in mind, we will, nevertheless, apply the Flesch Reading Ease Test to the aforementioned texts taken from the historical literature databases in order to check whether a diachronic drift on the model of Biber et al. can be identified.

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