Robin van Rijthoven

64 Chapter 3 In this phase of the intervention, children also read polysyllabic words and thus needed to understand that the third and fourth spelling rules also apply to reading. The word ‘ramen’ shows a short vowel but it needs to be read as a long vowel (/raa-men/) andwhen a double consonant is sighted the vowel can be read short as well, but the consonant must be read only once (/ki-pen/). Additional rules for spelling and reading were taught according to each child’s needs. In order to rehearse the above-mentioned spelling and reading knowledge children had to do some home exercises both for reading as well as spelling. Parents were asked to train four times a week during 15 minutes with prescribed exercises. Parents kept a log, provided by the clinician. Based on this log, the clinician could move forward or give more attention to certain topics. When a child reached an accuracy of 80% during practice (read or write 80% of the words correctly) and improved significant in their fluency (more fluent compared to the first time words were read) the clinician moved on to the next topic or phase of intervention. Therefore, variation in the length of the program is present. Analytic approach All outcome measures were measured before and after the intervention and both pre- and posttest scores were standardized compared to norm-based peers using percentile scores at the time of testing. We calculated the individual mean change per session (bothwith rawand percentile scores) by subtracting pre- fromposttest scores. Following Gollwitzer and colleagues (2014) change scores are reliable if two requirements are met. First, standard deviations must differ between measurement occasions. Second, there needs to be a non-zero variation in observed difference scores in order to define the reliability. In order to rule out the effects of variation in the length of the intervention, the individual change score was divided by the number of sessions the intervention for each individual lasted. Working with change scores implied that the differences in individual pretest scores were not taken into account. Pretest scores were included as a control variable to control for variation. Results Descriptive statistics Table 3.1 presents the descriptive statistics (means, standard deviations, and range) of all study measures. Both pre- and posttest scores are given of all outcome measures in raw scores and percentile scores. These percentiles scores are based on norms within the typically developing population. At the start of the intervention the mean scores were below the 10th percentile on pseudoword reading, word reading, and word