Validation methods to measure textbooks readability

The purpose of this study is to strengthen the applied literature and present the objective computational sample of measure textbooks readability. This article is more than introducing existing methods. Measuring textbooks readability of the fourth and fifth grade of elementary schools reading books have been done by using the international prevalent computing methods of readability like: Flesch, Fry, Gunning, McLaughlin, Flesch–Kincaid, Powers-Sumner-Kearl to compare the results of these different methods then the validity of them was done. It is an analytical research in the type of evaluation. The findings showed that results of Flesch and Fry methods were similar and in both methods evaluated books were in accordance with their grades of elementary schools. The results of Gunning and McLaughlin methods in both grades of elementary schools were similar and they determined that “Reading Book” of the fourth grade is suitable for the first grade of the junior school and “Reading Book” of the fifth grade is suitable for the third grade of the junior school. The Powers-Sumner-Kearl and Flesch–Kincaid methods had less resolution as Powers-Sumner-Kearl method showed that both books in the fourth and fifth grades are appropriate for the second grade of junior school and the Flesch–Kincaid method illustrated that they are both appropriate for the first grade of high school. Therefore the Flesch and Fry methods have been the most coordinate with the current educational “Reading books” in the fourth and fifth grades of elementary school.