Adding practical tools to our toolbox: introduction to the special issue on quantitative methodologies.

The most recent special issue in the Journal of Pediatric Psychology devoted to methodologies was published more than a decade ago (Noll, 2002). Several articles in that issue focused explicitly on quantitative methodologies. These articles were well-received by and influential within the specific discipline of pediatric psychology and the broader academic community (Aylward, Roberts, Colombo, & Steele, 2008). Owing to, in no small part, the 2002 special issue (Noll, 2002), the field of Pediatric Psychology has continued to mature with regard to methodological and statistical sophistication. Since the 2002 special issue, several important articles on quantitative methodologies were published in the Journal of Pediatric Psychology. These articles include practical coverage of topics such as growth curve modeling (Delucia & Pitts, 2006), analysis of count data (Karazsia & van Dulmen, 2008), effect sizes (Durlak, 2009), structural equation modeling (Nelson, Aylward, & Steele, 2008), and time-window sequential analysis (MacLarenChorney, Garcia, Berlin, Bakeman, & Kain, 2010). This special issue can be viewed as a supplement to such works. Another sign of the field embracing quantitative methods is the recently formed PRISM Special Interest Group, whose members have interests in Pediatric Research and Innovative Statistical Methodologies (Karazsia & Berlin, 2013). As part of our roles as PRISM SIG Co-Chairs, we believed it was time for another issue focused on accessible introductions to quantitative methods that have relevance to pediatric psychologists. With this in mind, our charges to authors in this issue were as follows: (a) write articles as a practical resource or guide, using straightforward language that will promote adoption of techniques by applied researchers; (b) include practical illustrations of methods, preferably with realworld data; and (c) include annotated syntax where appropriate to supplement the illustration. Invited authors for this issue not only answered this call, but they went above and beyond to present complex topics in ways that will resonate with pediatric scholars. The enthusiasm that authors brought to their work is illustrated in the titles. Who, other than Todd Little, would title an article about missing data ‘‘On the Joys of Missing data . ’’ (emphasis added; Little, Jorgensen, Lang, & Moore, 2014). While many scholars may dread the issue of missing data, Little, Jorgensen, Lang, and Moore (2014) illustrate proactive methodological strategies that can minimize or prevent the problem when considered before data collection commences. Another example is Eric Youngstrom’s calling the field to ‘‘ROC’’ (Receiver Operator Characteristic) with him (Youngstrom, 2014, ‘‘We are Ready to ROC’’). In his coverage of ROC analyses, Youngstrom (2014) illustrates the intricate relations between real-world issues faced by practicing clinicians, the questions researchers ask, and the quantitative methods that can help answer those questions and yield clinically relevant results. Two articles in this issue serve as complements to recent calls within the field for more single-subject studies (e.g., Rapoff, 2010) by introducing quantitative approaches to analyzing data from such designs (Cohen, Feinstein, Masuda, & Vowles, 2014; Cushing, 2014). These articles also highlight the relevance of pediatric research within real-world clinical practice settings. Cohen, Feinstein, Masuda, and Vowles (2014) wrestle with the fact that