Search

Snowball designs are the most natural of the network sampling designs. They have many desirable properties for sampling hidden and hard-to reach populations. They have been under-used in recent years because simple design-based estimators and confidence intervals have not been available for them. The needed estimation methods are supplied in this paper. Snowball sampling methods and accurate estimators with them are needed for sampling of the people exposed to the animals from which new coronavirus outbreaks originate, and to sample the animal populations to which they are exposed. Accurate estimates are needed to evaluate the effectiveness of interventions to reduce the risk to the people exposed to the animals. In this way the frequencies of major outbreaks and pandemics can be reduced. Snowball designs are needed in studies of sexual and opioid networks through which HIV can spread explosively, so that prevention intervention methods can be developed, accurately assessed, and effectively distributed., Comment: arXiv admin note: text overlap with arXiv:2002.01350

Network sampling is used around the world for surveys of vulnerable, hard-to-reach populations including people at risk for HIV, opioid misuse, and emerging epidemics. The sampling methods include tracing social links to add new people to the sample. Current estimates from these surveys are inaccurate, with large biases and mean squared errors and unreliable confidence intervals. New estimators are introduced here which eliminate almost all of the bias, have much lower mean squared error, and enable confidence intervals with good properties. The improvement is attained by avoiding unrealistic assumptions about the population network and the design, instead using the topology of the sample network data together with the sampling design actually used. In simulations using the real network of an at-risk population, the new estimates eliminate almost all the bias and have mean squared-errors that are 2 to 92 times lower than those of current estimators. The new estimators are effective with a wide variety of network designs including those with strongly restricted branching such as Respondent-Driven Sampling and freely branching designs such as Snowball Sampling., Comment: arXiv admin note: substantial text overlap with arXiv:1909.05018

Network surveys of key populations at risk for HIV are an essential part of the effort to understand how the epidemic spreads and how it can be prevented. Estimation of population values from the sample data has been probematical, however, because the link-tracing of the network surveys includes different people in the sample with unequal probabilities, and these inclusion probabilities have to be estimated accurately to avoid large biases in survey estimates. A new approach to estimation is introduced here, based on resampling the sample network many times using a design that adheres to main features of the design used in the field. These features include network link tracing, branching, and without-replacement sampling. The frequency that a person is included in the resamples is used to estimate the inclusion probability for each person in the original sample, and these estimates of inclusion probabilities are used in an unequal-probability estimator. In simulations using a population of drug users, sex workers, and their partners for which the actual values of population characteristics are known, the design-adherent estimation approach increases the accuracy of estimates of population quantities, largely by eliminating most of the biases.

A new estimation method is presented for network sampling designs, including Respondent Driven Sampling (RDS) and Snowball (SB) sampling. These types of link-tracing designs are essential for studies of hidden populations, such as people at risk for HIV. The simple idea behind the new method is to run a fast-sampling process on the sample network data to estimate the inclusion probabilities of the actual survey, and incorporate those in unequal probability estimators of population means and proportions. Improved versions of the usual RDS and SB designs are also proposed, termed RDS+ and SB+, to obtain information on more of the within-sample links. In simulations using the network from the Colorado Springs study on the heterosexual spread of HIV, the new estimators produce in most cases lower bias and lower mean square than current methods. For the variables having the largest mean square errors with current estimators, the improvement with the new estimator is dramatic. The estimates are improved even more with the enhanced design versions. For estimating the population mean degree, the efficiency gains using he new method are 29 for RDS, 54 for RDS+, 26 for SB and 80 for SB+. This means for example, with the ordinary RDS design, the mean square error with the new estimator, same data, is 1/29 that of currently used estimators. The new method is computationally intricate but is fast and scales up well. The new estimation method can be used to re-analyze existing network survey data. For new network sampling studies, it is recommended to use the improved designs as well as the new estimators.

A new strategy is introduced for estimating population size and networked population characteristics. Sample selection is based on a multi-wave snowball sampling design. A generalized stochastic block model is posited for the population's network graph. Inference is based on a Bayesian data augmentation procedure. Applications are provided to an empirical and simulated populations. The results demonstrate that statistically efficient estimates of the size and distribution of the population can be achieved.

This qualitative study investigated perceptions of contemporary leaders regarding moral and ethical learning and the role of higher education. There were three steps in the data collection procedures: a survey of graduate students, open-ended interviews with the selected leaders, and document content analysis. Participants were asked whether they believed individuals can be educated to be moral and ethical, and if so, how they perceived that this could be achieved. Findings indicated participants believe people can be educated to be moral and ethical. Participants suggested ways that universities might assist students to reach a greater moral potential. Suggestions focused on teaching, the value of service learning, and university courses. Conclusions point to community service and field experiences as vital for moral education and indicate that those who receive a more generalized education--liberal arts--will be better equipped for moral development and leadership than specialists.

This qualitative study conducted in urban Miami, Florida, explored the essence of juvenile delinquency and recidivism: its causes, its relations to communities, the roles of families, and the myriad roles of residential treatment programs at rehabilitating young offenders. Data were collected from nine young adult participants who had satisfied their court-ordered sanctions in different residential facilities. Data were analyzed to discover themes, patterns, or clusters of meanings. Six themes emerged. These included varying perspectives, overcoming patterns of delinquent behaviors, challenges of remaining focused and goal-oriented, suggestions for young offenders, recommendations for change to correctional leaders, and accounts of their successes and failures. The following assumption was reported by participants: young offenders who have supportive familial relationships, who function as productive citizens within their communities, and who make satisfactory performance in school, may experience recidivism less frequently than those who exhibit opposite characteristics. Findings also suggested that poverty, peer relations, school, family life, self-imposed limitations, and community dynamics were linked to juvenile offending. Implications are included for lawmakers, criminologists, and juvenile justice administrators as measures for reducing juvenile delinquency and recidivism. The following are appended: (1) Participant Demographic and Delinquent History; and (2) Interview.

Amid various educational options, there are certain groups of parents who choose to send their children to military-styled boarding schools. There is abundant scholarly literature addressing traditional boarding schools but a paucity of extant, relevant literature specific to the choice of military boarding schools as an educational option. This qualitative study investigated why parents opt to send their sons to military boarding schools in lieu of traditional boarding schools. A purposeful sample of twelve parents who had sent their sons to military-styled boarding schools participated in the study. Data collection and analysis followed from open-ended, semi-structured interviews. Findings indicated that parents had desired outcomes for their sons including discipline, structure, responsibility, self-sufficiency, and college preparation. In addition to self-governance and self-discipline, some parents indicated a desire for their sons to be judged based on their own performance. Some parents stated they felt that traditional boarding schools provided an environment that was too relaxed on a disciplinary and structural level. Includes appendix with interview questions.

We present a new design and inference method for estimating population size of a hidden population best reached through a link-tracing design. The strategy involves the Rao-Blackwell Theorem applied to a sufficient statistic markedly different from the usual one that arises in sampling from a finite population. An empirical application is described. The result demonstrates that the strategy can efficiently incorporate adaptively selected members of the sample into the inference procedure., Comment: 23 pages, 2 tables, 4 figures

This qualitative case study investigated a large, suburban, public middle school focusing on educators' perceptions of leadership within their professional learning community. Participants included the principal, administrative team, and key faculty members. Data were collected using semi-structured interviews and were analyzed by hand coding and Nudist software. Findings indicated the principal has the ability to recognize leadership qualities in others, the school's mission/vision is connected to student learning, a leadership team supports and maintains the professional learning community, communication and collaboration are important to a professional learning community, coaching and mentoring assist in developing teachers and empowering others to take leadership roles, and the development of a learning organization promotes growth, learning, and empowerment opportunities for all. This study contributes to the literature relating to educational administration. The researchers hope that the findings of this study will assist school administrators and educators in their understanding of the leadership characteristics of a professional learning community. This study also contributes to the literature by providing real-life examples of transformational leadership in action. The leadership of the principal has a tremendous impact on the viability and success of the school. Principals may also use this information to make school reforms more successful and create structures within their schools that enhance communication and collaboration around shared norms and values. Appended are: (1) Principal Interview Protocol; (2) Administrative Team Interview Protocol; and (3) Key Faculty Member Interview Protocol.