Introduction to Sample Size Choice for Confidence Intervals Based on t Statistics

Sample size can be chosen to achieve a specified width in a confidence interval. The probability of obtaining a narrow width given that the confidence interval includes the population parameter is defined as the power of the confidence interval, a concept unfamiliar to many practitioners. This article shows how to utilize the Statistical Analysis System (SAS) proc power procedure to determine an appropriate sample size and achieve sufficient power for a specified confidence interval. Two examples in sport and exercise science are used to illustrate sample size determination for confidence intervals in the dependent and independent t tests. The relevant SAS code and output are provided with detailed annotations. As the use of confidence intervals becomes a more integral part of studies in sport and exercise science, the reporting and analysis of their power should be considered much like that of hypothesis tests.     

Geography in school and college

Joe Russell Whitaker. Geography in School and College, Bureau of Publications. George Peabody College for Teachers, Nashville, Tennessee, 1948 pp. 116 $1.80     

Biodeterioration of Incralac used for the protection of bronze monuments

Outdoor bronze sculptures are highly susceptible to corrosion in many environments and organic coatings are widely used for their protection. The purpose of this study was to determine the susceptibility of the commonly used coating Incralac to biodeterioration by microorganisms. A yeast was isolated from a bronze statue treated with Incralac and its ability to degrade Incralac was determined using growth curves, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The organism grew slowly on Incralac in liquid culture, but SEM images demonstrated its ability to adhere to Incralac coated metal. Additionally, the yeast caused a rapid drop in the low frequency impedance of Incralac coated metal that was not observed under sterile conditions, indicating that the organism accelerated deterioration of the coating. The potential for microbial growth to accelerate deterioration of Incralac should be considered when developing a maintenance strategy for the protection of outdoor metal monuments.     

To Catch a Liar: Challenges for Research in Lie Detection Training

Can we train people to detect deception? It is the contention of this article that communication scholars should learn how to train law enforcement professionals on how to detect high stake lies, like those faced by police, judges, customs officials, immigration officials, and so forth. It is proposed that in order to know whether we can train or should bother to train people to detect deception, each training study must meet 6 challenges: (1) relevance, (2) high stakes, (3) proper training, (4) proper testing, (5) generalizability across situations, and (6) generalizability over time. Our quantitative review of the literature suggests that training does significantly raise lie detection accuracy rates. Meta-analytic findings indicate a mean effect size of r = .20 across 20 (11 published studies) paired comparisons of lie detection training versus the control group (i.e., those without some type of training). It should be noted that the majority of the studies that attempt to train lie detectors fall short on many of the above challenges. Current research in lie detection training may actually underestimate the ability to train lie detectors due to the stimulus materials employed in most experiments.     

Interactive Influences of Perceived Social Contexts on the Reading Achievement of Urban Middle Schoolers with Learning Disabilities

This study examined the effects of social influences in the lives of an ethnically diverse sample of fifth through eighth grade students with and without learning disabilities (LD) using survey data and academic achievement scores collected in 19 Chicago public schools from 1993–1997. Similarities and differences in student perceptions of school, family, and peer group contexts were examined. In addition, longitudinal data were analyzed using hierarchical linear modeling (HLM) to identify contextual influences on changes in student reading achievement over time. Comparisons of student responses confirm and extend existing findings in the literature concerning the perceptions of students with LD of their social environments. In particular, having a learning disability was associated with consistent, mostly negative, effects on social relations across the contexts of students’ lives, regardless of gender, race, grade, and socioeconomic status. In addition, student perceptions of their friendship groups were found to have small, but significant, effects on their growth in reading achievement over the course of middle school. While students with and without LD had somewhat different views of their social contexts, the processes working within these environments appeared to affect their reading achievement in similar ways. The results suggest that careful attention should be paid to the social contexts of students’ lives when planning academic interventions.