A Practical Guide to Calculating Cohen’s f2, a Measure of Local Effect Size, from PROC MIXED

Reporting effect sizes in scientific articles is increasingly widespread and encouraged by journals; however, choosing an effect size for analyses such as mixed-effects regression modeling and hierarchical linear modeling can be difficult. One relatively uncommon, but very informative, standardized measure of effect size is Cohen’s f2, which allows an evaluation of local effect size, i.e., one variable’s effect size within the context of a multivariate regression model. Unfortunately, this measure is often not readily accessible from commonly used software for repeated-measures or hierarchical data analysis. In this guide, we illustrate how to extract Cohen’s f2 for two variables within a mixed-effects regression model using PROC MIXED in SAS® software. Two examples of calculating Cohen’s f2 for different research questions are shown, using data from a longitudinal cohort study of smoking development in adolescents. This tutorial is designed to facilitate the calculation and reporting of effect sizes for single variables within mixed-effects multiple regression models, and is relevant for analyses of repeated-measures or hierarchical/multilevel data that are common in experimental psychology, observational research, and clinical or intervention studies

Confidence Disparities: Pre-course Coding Confidence Predicts Greater Statistics Intentions and Perceived Achievement in a Project-Based Introductory Statistics Course

AbstractSelf-efficacy is associated with a range of educational outcomes, including science and math degree attainment. Project-based statistics courses have the potential to increase students’ math self-efficacy because projects may represent a mastery experience, but students enter courses with preexisting math self-efficacy. This study explored associations between pre-course math confidence and coding confidence with post-course statistical intentions and perceived achievement among students in a project-based statistics course at 28 private and public colleges and universities between fall 2018 and winter 2020 (n = 801) using multilevel mixed-effects multivariate linear regression within multiply imputed data with a cross-validation approach (testing n = 508 at 20 colleges/universities). We found that pre-course coding confidence was associated with, respectively, 9 points greater post-course statistical intentions and 10 points greater perceived achievement on a scale 0–100 (0.09, 95% confidence interval (0.02, 0.17), p = 0.02; 0.10, 95% CI (0.01, 0.19), p = 0.04), and that minoritized students have greater post-course statistical intentions than nonminoritized students. These results concur with past research showing the potential effectiveness of the project-based approach for increasing the interest of minoritized students in statistics. Pre-course interventions to increase coding confidence such as pre-college coding experiences may improve students’ post-course motivations and perceived achievement in a project-based course. Supplementary materials for this article are available online

The imaginary companion phenomenon: an analysis of personality correlates and developmental antecedents

p. 220-228In the present studies, both the incidence of recall of an imaginary companion and the remembered vividness of the experience were assessed in college students. The purpose of the research was to ascertain the extent to which individuals in a non clinical population who recall having a childhood imaginary companion share characteristics and negative life experiences with individuals diagnosed with Dissociative Identity Disorder (DID) ; in this clinical group childhood imaginary companions are reported fairly frequently, and the experience is described as extremely vivid (Sanders, 1992). Two studies were carried out, In Study 1, students of both sexes who remembered an imaginary companion (IC+) were found to be more dissociative than those who reported not having a companion (IC I). The IC+ women also scored higher on an imaginative Involvement Inventory than IC- women. This difference did not reach statistical significance among the male students. Study 2 screened a new population of female students in order to compare three groups of women: A High Vividness group (PM, a Low Vividness group (LV), and a no-companion group (IC-). The HV group was comprised of IC+ women who said they had been able to see and hear their childhood imaginary companion, and who remembered believing the companion was real; the LV group consisted of IC+ women who answered "no " to these 3 vividness questions, and the IC- group was defined as in Study 1. The HV women were found to be significantly higher in imaginative involvement than the LV group, and also more dissociative. The LV group did not differ significantly from the IC - group. In both studies, students who reported remembering an imaginary companion, even those whose experience was perceptually vivid, did not report significantly more lonely, stressful or traumatic childhoods than comparison groups

Does number of lifetime traumas explain the relationship between PTSD and chronic medical conditions? Answers from the National Comorbidity Survey-Replication (NCS-R)

Photograph of Red Bud Trees, the official State Tree of Oklahoma, in bloom, in Eastern Oklahoma

Ethnic differences in weight control practices among U.S. adolescents from 1995-2005

Objective: To examine trends in weight control practices from 1995 to 2005. Method: The Youth Risk Behavior Surveillance System biennially assesses five weight control behaviors among nationally representative samples of United States high school students. Results: Across time, more females than males dieted (53.8% vs. 23.8%), used diet products (10% vs. 4.3%), purged (7.5% vs. 2.7%), exercised (66.5% vs. 46.9%), or vigorously exercised (42.8% vs. 36.8%). All weight control behaviors among males increased during the decade. Black females were less likely than Hispanic females, who were less likely than White females, to practice weight control. White males were less likely than Black males, who were less likely than Hispanic males, to practice weight control. The ethnic difference in weight control practices is consistent across time. Conclusion: All male adolescents are at increasing risk for developing eating disorder symptomatology, and Black females appear to continue to resist pressure to pursue thinness. © 2007 by Wiley Periodicals, Inc. Int J Eat Disord 200