A longitudinal study of adolescent educational aspirations and their relationship to college choice using hierarchical linear modeling and group-based mixture modeling

The purpose of this study was four-fold: (1) to investigate the patterns of change in educational aspirations from the eighth grade through the twelfth in a large national sample of students from the National Educational Longitudinal Survey of 1988 (NELS:88); (2) to understand how demographic, socioeconomic, parental, academic, and school experience factors impact both initial aspirations and change in aspirations; (3) to investigate how educational aspirations relate to students’ attempts to actualize plans for postsecondary education; and (4) to analyze the data and compare the results obtained using two different growth modeling techniques – hierarchical linear modeling and group-based mixture modeling. Major findings of the study showed that (1) average student aspirations remained fairly stable from the eighth grade through the twelfth, showing a slight but not significant increase; (2) most of the factors considered in the study affected initial student aspirations; (3) seven distinct clusters of aspiration trajectories can be identified; (4) many students who had high aspirations had failed to build a wide choice set of postsecondary institutions to apply to; (5) among the factors considered, educational aspirations had the strongest impact on the number of applications filed; (6) parental expectations and involvement had effects on early student aspirations but not on the number of applications filed; (9) students who had both high and stable aspirations from the eighth grade through the twelfth generally had a wider choice set of applications than students who demonstrated a steady increase in aspirations. Hierarchical linear modeling provided an understanding of the average growth in aspirations, the variability around that growth and the effects of covariates on initial aspirations and the change in aspirations. Group-based mixture modeling helped investigate the different clusters of aspiration trajectories and permitted a linkage of these clusters with patterns of student application to postsecondary institutions. The link between aspirations and the number of college applications filed was studied using modeling for ordinal responses. The strengths of the different modeling techniques are addressed and implications of the results for educational policy, practice, and future research are also discussed

Statistical Analysis of Peptide-Induced Graded and All-or-None Fluxes in Giant Vesicles

AbstractAntimicrobial, cytolytic, and cell-penetrating peptides induce pores or perturbations in phospholipid membranes that result in fluxes of dyes into or out of lipid vesicles. Here we examine the fluxes induced by four of these membrane-active peptides in giant unilamellar vesicles. The type of flux is determined from the modality of the distributions of vesicles as a function of their dye content using the statistical Hartigan dip test. Graded and all-or-none fluxes correspond to unimodal and bimodal distributions, respectively. To understand how these distributions arise, we perform Monte Carlo simulations of peptide-induced dye flux into vesicles using a very simple model. The modality of the distributions depends on the rate constants of pore opening and closing, and dye flux. If the rate constants of pore opening and closing are both much smaller than that of dye flux through the pore, all-or-none influx occurs. However, if one of them, especially the rate constant for pore opening, increases significantly relative to the flux rate constant, the process becomes graded. In the experiments, we find that the flux type is the same in giant and large vesicles, for all peptides except one. But this one exception indicates that the flux type cannot be used to unambiguously predict the mechanism of membrane permeabilization by the peptides