Empirical Verification of the Polish Formula of Text DifficultyThe aim of the study was to verify the accuracy of the formula for assessing the difficulty of texts written in Polish (Pisarek 1969). The study involved 1,309 persons aged between 15 and 84. 15 texts were used, each approximately 300 words long, representing different subjects and varied difficulty level. Text comprehension was checked with multiple choice tests, the cloze procedure and open-ended questions. Significant correlations between the difficulty of a text and its comprehension were found (rmc(15) = -0.529, p = 0.043; ropen = -0.519, p = 0.047; rcloze = -0.656, p = 0.008). The results confirmed relative accuracy and usefulness of Pisarek's readability formula. The discussion includes proposed ways of improving the current form of the formula.