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.     

Game location and aggression in rugby league

The present study examined the relationship between aggression and game location in rugby league. We videotaped a random sample of 21 professional rugby league games played in the 2000 Super League season. Trained observers recorded the frequency of aggressive behaviours. Consistent with previous research, which used territoriality theories as a basis for prediction, we hypothesized that the home team would behave more aggressively than the away team. The results showed no significant difference in the frequency of aggressive behaviours exhibited by the home and away teams. However, the away teams engaged in substantially more aggressive behaviours in games they lost compared with games they won. No significant differences in the pattern of aggressive behaviours for home and away teams emerged as a function of game time (i.e. first or second half) or game situation (i.e. when teams were winning, losing or drawing). The findings suggest that while home and away teams do not display different levels of aggression, the cost of behaving aggressively (in terms of game outcome) may be greater for the away team.     

Pathways of China's PM2.5 air quality 2015-2060 in the context of carbon neutrality

Clean air policies in China have substantially reduced particulate matter (PM2.5) air pollution in recent years,primarily by curbing end-of-pipe emissions.Howev...     

Environmental identity,pro-environmental behaviors,and civic engagement of volunteer stewards in Portland area parks

We conducted surveys of adults participating in municipally sponsored volunteer events in the Portland, OR metropolitan area in order to understand the range of attitudes and behaviors associated with volunteer work. We sampled 172 individuals in 18 events from February to June 2012. Principal components and factor analyses of survey responses identified three groups based on annual frequency of participation in stewardship events: first-time volunteers, mid-level volunteers (3–10 events per year), and frequent volunteers (>10 events per year). Our analyses revealed three main factors that explained the variation in survey response for the three volunteer groups: environmental identity, private pro-environmental behavior, and civic engagement. All three factors were positively correlated with frequency of participation in stewardship events, with the most frequent volunteers indicating the highest degree of attention to environmental issues, environmental identity, and self-reported pro-environmental behaviors. Frequent volunteers were more likely to feel personally attached to their local environment, believe that their efforts help solve environmental problems, and enjoy being part of community efforts. These results suggest that stewardship activities provide opportunities for volunteers to interact with others while working collectively toward restoring and maintaining parks, which may contribute to more resilient communities.     

Teacher Perceptions of School Consultant Social Influence Strategies: Replication and Expansion

The goals were to (a) replicate the findings of previous research with regard to the Consultee/Teacher Version of the Interpersonal Power Inventory (IPI), and (b) advance the literature by examining IPI scores about a current consultation relationship. Sample 1 included 99 elementary school teachers (44.4% Hispanic) who completed the IPI. Results replicated Erchul et al. Sample 2 (N = 37; 45.9% Hispanic) represented a subset of Sample 1 who participated in a consultation project and completed the IPI about influence in their current consultation relationship. The results advance the literature by offering evidence for convergent and predictive validity of the IPI soft power bases. Teachers who reported being influenced by soft power strategies experienced greater change in their behaviors and their students’ behaviors than those who reported being not influenced by such strategies. Implications for research and practice in school consultation are discussed.