CHAPTER 7 168 task difficulties, rater severities, and item difficulties, is adopted by default as the 0 point. To interpret, person locations are plotted so that any persons has a 50% probability of succeeding with an item located at the same point on the logit scale. For example, a person with an ability estimate of 0 logits has a 50% probability of succeeding (or failing) on an item which has a difficulty estimate of 0 logits. That same person would have a greater than 50% chance of succeeding on items less difficult than logits and less than a 50% probability of succeeding on items that are more difficult 0 logits. Next, each PRPP item was examined for “fit” with the Rasch mathematical model, considering both infit and outfit, as mean square values and standardized z-scores. For clinical observations, a mean-square range of 0.5 – 1.7 is considered acceptable, with normalized z-score[51]. Infit and outfit statistics are also reported in normalized form (z), where their expected value is 0, and standardized z values less than -2 or greater than +2 are generally interpreted as having less compatibility with the model than expected (p < 0.05). Negative values indicate less variation than modelled. While positive values indicate more variation than modelled, and greater than +2 means they are too erratic to be useful[50]. Generally, positive values are considered more problematic during interpretation. In addition, the Rasch calibrated hierarchy of 35 PRPP items (stage 2) was generated following the procedure of Bond & Fox[50]. Interaction plots constructed by FACETS were used to visually present the differences in efficiency of cognitive strategy application between the three. Due to the small sample size, between group analysis of variance was not performed. The article of Nott & Chapparo[26] can be used for more detailed information on analyzing PRPP-Assessment scores with Rasch. Ethical Considerations All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards[52]. The ethical board of the regional research committee provided their approval (ethical board approval number 2019-5493). All parents signed informed consent and all raters signed a confidentially agreement. Where indicated, the children also signed the informed consent to demonstrate their volition/agency[53].
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