The 4-H Study of Positive Youth Development (PYD), a longitudinal investigation of a diverse sample of 1,700 fifth graders and 1,117 of their parents, tests developmental contextual ideas linking PYD, youth contributions, and participation in community youth development (YD) programs, representing a key ecological asset. Using data from Wave 1 of the study, structural equation modeling procedures provided evidence for five first-order latent factors representing the "Five Cs" of PYD (competence, confidence, connection, character, and caring), and for their convergence on a second-order, PYD latent construct. A theoretical construct, youth "contribution," was also created and examined. Both PYD and YD program participation independently related to contribution. The importance of longitudinal analyses for extending the present results is discussed. 2The 4-H Study of Positive Youth Development (PYD) is a longitudinal investigation that seeks to identify the individual and ecological bases of healthy, positive development among diverse adolescents. Framed by an instance of developmental systems theory, developmental contextualism (Lerner, 2002(Lerner, , 2004, the 4-H Study is designed to follow youth across the second decade of life and to examine their developmental trajectories. This article describes the theoretical and methodological components of the study, and reports some key findings derived from the first wave of data collection (which occurred in 2002-2003).While we present the theoretical and empirical literature that legitimates the structural model and the design of the study, and in turn provide details about all features of the measurement model, we do not present analyses pertinent to all research questions, particularly since key facets of this model are optimally tested with change-sensitive data that will be available only through subsequent, longitudinal waves of the study. Instead, we present findings pertinent to the presence and structure of the several characteristics presently focused on in the literature as composing PYD (i.e., the Five "C"s of competence, confidence, character, connection, and caring) (e.g., Eccles & Gootman, 2002). We also propose a theoretical measure of youth contribution appropriate for early adolescents and examine unitemporal patterns of covariation with the 5Cs.Simply, before we could test with longitudinal data our developmental contextual conception of the process through which PYD occurs, we needed to establish that the concept of PYD as it had been discussed in the literature had empirical reality, both in its purposed structure and its covariation with other key individual and ecological variables 2 . Accordingly, we address the question of whether in the present data set there is evidence for the theoretical expectations that PYD is positively related to contribution and negatively related to adolescent risk and 3 problem behaviors and, as well, whether there is an association between PYD and youth participation in community-based, youth development (Y...

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Developmental science rests on describing, explaining, and optimizing intraindividual changes and, hence, empirically requires longitudinal research. Problems of missing data arise in most longitudinal studies, thus creating challenges for interpreting the substance and structure of intraindividual change. Using a sample of reports of longitudinal studies obtained from three flagship developmental journals-Child Development, Developmental Psychology, and Journal of Research on Adolescence-we examined the number of longitudinal studies reporting missing data and the missing data techniques used. Of the 100 longitudinal studies sampled, 57 either reported having missing data or had discrepancies in sample sizes reported for different analyses. The majority of these studies (82%) used missing data techniques that are statistically problematic (either listwise deletion or pairwise deletion) and not among the methods recommended by statisticians (i.e., the direct maximum likelihood method and the multiple imputation method). Implications of these results for developmental theory and application, and the need for understanding the consequences of using statistically inappropriate missing data techniques with actual longitudinal data sets, are discussed.

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