Abstract
The impact of fluency and comprehension on mathematical word problem solving is explored using data on fifth-graders who took part in the German National Educational Panel Study (NEPS). The Multiple Deficit Model (MDM) suggests that the impact of fluency and comprehension on mathematical word problem solving should be the same for students with and without dyslexia, even if they are at different levels in reading and mathematics. This study shows that students with poor fluency or comprehension score lower in word problems than typical readers. For all students with reading difficulties, the impact of fluency on mathematical performance is less than it is for typical readers. For students with deficits in either comprehension or fluency alone, the impact of comprehension on word problem solving is the same as for typical readers. But the impact of comprehension is less if the students are weak in both fluency and comprehension, which, according to the MDM, suggests the presence of additional or different underlying cognitive deficits. While students with poor fluency can compensate for this deficit with reading comprehension, students with poor comprehension cannot compensate with fluency. Comprehension has a larger impact on mathematical word problem solving than fluency.