Browsing by Subject "Longitudinal studies"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item An examination of identity formation during adolescence: a person-oriented appraoch(Texas Tech University, 1999-08) Forthun, Larry F.The purpose of this research was to study the formation of a sense of identity during adolescence longitudinally, psychosocially, and developmentally. Based on the evidence that has accumulated over the past several decades, it was reasonable to conclude (a) that exploration and commitment are important processes in identity formation (e.g., Marcia's idendty status model), (b) that the process of forming an identity cannot be divorced from the context in which it occurs, and (c) that it is important to understand how adolescents respond to identity challenging information. The current study addressed each of these components by combining a longitudinal investigation of adolescents who were experiencing identity-relevant disruptions with a person-oriented developmental perspective. A sample of 20 adolescents were followed throughout their participation in a community based after-school program. The purpose of this study was not to evaluate the program; rather, to examine identity developmental processes among a group of adolescents who were experiencing identity-relevant disruptions in their lives. Each adolescent was interviewed at the beginning and end of their participation in the program using the Groningen Identity Development Scale. Using a qualitative analytical strategy, eight subgroups of adolescents were discriminated based upon variations in the configuration of identity relevant characteristics. The groups were discriminated based on themes of strength and congruence of commitments in identity relevant domains, level of exploration and openness to experience, the degree of attachment to parents, the degree of validation and belonging with peers, the adoption of a relevant belief system to guide their behavior (e.g., an ideology), and commitment to future scholastic and/or occupational goals. Supplemental questionnaires were also completed by the participants in this study and repeated measures ANOVAs suggest that the subgroups differed in the expected direction on many of the measures. Although the findings are not inconsistent with Marcia's identity status model, the adoption of a person-oriented developmental perspective allows the key concepts of commitment and exploration to be integrated with contemporary empirical and theoretical notions regarding identity formation without sacrificing a person-centered orientation.Item Approaches to modeling self-rated health in longitudinal studies : best practices and recommendations for multilevel models(2012-05) Sasson, Isaac; Powers, Daniel A.; Umberson, Debra J.Self-rated health (SRH) is an outcome commonly studied by demographers, epidemiologists, and sociologists of health, typically measured using an ordinal scale. SRH is analyzed in cross-sectional and longitudinal studies for both descriptive and inferential purposes, and has been shown to have significant validity with regard to predicting mortality. Despite the wide spread use of this measure, only limited attention is explicitly given to its unique attributes in the case of longitudinal studies. While self-rated health is assumed to represent a latent continuous and dynamic process, SRH is actually measured discretely and asymmetrically. Thus, the validity of methods ignoring the scale of measurement remains questionable. We compare three approaches to modeling SRH with repeated measures over time: linear multilevel models (MLM or LGM), including corrections for non-normality; and marginal and conditional ordered-logit models for longitudinal data. The models are compared using simulated data and illustrated with results from the Health and Retirement Study. We find that marginal and conditional models result in very different interpretations, but that conditional linear and non-linear models result in similar substantive conclusions, albeit with some loss of power in the linear case. In conclusion, we suggest guidelines for modeling self-rated health and similar ordinal outcomes in longitudinal studies.Item Longitudinal effects of working memory on internalizing and externalizing behavior problems(2010-08) Low, Justin Alan; Keith, Timothy, 1952-; Tharinger, Deborah; Carlson, Cindy; Beretvas, Susan; Anderson, EdwardSeveral research studies have examined the link between working memory ability and behavior problems in youth. Research suggests that children with working memory deficits demonstrate lower levels of attention and higher levels of hyperactivity, physical aggression, and other behavior problems. The purpose of this research was to determine the effects of developmental trajectories of working memory on the developmental trajectories of behavior problems. Results suggested that developmental increases in working memory did not lead to developmental decreases in behavior problems. Results from this study suggested that internalizing and externalizing behavior problems increase over the course of childhood. Several variables did lead to developmental change in behavior problems in children. Children who had lower initial levels of working memory increased in internalizing behaviors less than children with higher initial working memory ability. Also, high socioeconomic status led to smaller increases in internalizing and externalizing behavior, high Peabody Picture Vocabulary Test (PPVT) scores led to larger increases in internalizing and externalizing behavior, and high PPVT scores led to larger decreases in inattentive and hyperactive behavior. Results are discussed in reference to current theories about working memory and behavior problems.Item Rank based methods in the factorial designs for longitudinal data with application to liver cancer studies(Texas Tech University, 2004-05) Gao, YuqingThe purpose of this research is to apply the rank based method (nonparametric method) in the factorial designs for longitudinai data with application to liver cancer studies. The hypotheses and test statistics are introduced for average group effect, average time effect, simple time effect, and the interaction between time and group. Two nonparametric models, Fl-LD-Fl model and LD-Fl model, are used to test the efficacy of green tea polyphnois (GTP) in reducing the concentration of aflatoxin Bl (AFBl) in blood samples and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urine samples. The results of this research could be a way to improve the chemoprevention in liver cancer.