Relative Distribution Methods

We present an outline of relative distribution methods, with an application to recent changes in the U.S. wage distribution. Relative distribution methods are a nonparametric statistical framework for analyzing data in a fully distributional context. The framework combines the graphical tools of exploratory data analysis with statistical summaries, decomposition, and inference. The relative distribution is similar to a density ratio. It is technically defined as the random variable obtained by transforming a variable from a comparison group by the cumulative distribution function (CDF) of that variable for a reference group. This transformation produces a set of observations, the relative data, that represent the rank of the original comparison value in terms of the reference group's CDF. The density and CDF of the relative data can therefore be used to fully represent and analyze distributional differences. Analysis can move beyond comparisons of means and variances to tap the detailed information inherent in distributions. The analytic framework is general and flexible, as the relative density is decomposable into the effect of location and shape differences, and into effects that represent both compositional changes in covariates, and changes in the covariate-outcome variable relationship.     

Explaining Late Life Urban vs. Rural Health Discrepancies in Beijing

Social characteristics that differ by place of residence are consequential for health. To study implications of this among older adults in rural vs. urban China, this study employs data from the Beijing municipality, a region that has witnessed growth and gaps in development. Life and active life expectancy is assessed using a multistate life table technique that estimates hazard rates and subsequent expected years in various health states. Hazards are estimated for a model that adjusts regional differences for age and sex and for a series of other models including additional covariates. Results indicate urban residents have an advantage. Specific factors show socio-economic status and access to health service account for a large part, social support and health behaviors for little, while disease is a suppressor.     

The geography of deterrence: exploring the small area effects of sobriety checkpoints on alcohol-impaired collision rates within a city

This article examines alcohol-impaired collision metrics around nine sobriety checkpoint locations in Indianapolis, Indiana, before and after implementation of 22 checkpoints, using a pre/post examination, a pre/post nonequivalent comparison group analysis, and an interrupted time series approach. Traffic safety officials used geographical information system (GIS) analysis to help select checkpoint locations amid high alcohol-related collision clusters, then analyzed possible checkpoint impacts. A post hoc analysis examined counts and rates of impaired collisions before and after checkpoint dates within the 2-mile radius zones around each checkpoint site and compared pre-to-post differences to two similar time-matched control areas without checkpoints. As a group, checkpoint zones showed significant though minor declines in pre-to-post collision counts, and no impairment rate change. Considered together, non-downtown checkpoint zones had more favorable impairment rates than comparison areas. After controlling for collision volume, monthly trend, and locational effects, the interrupted time series analysis found that for all checkpoints the count of impaired collisions in post-checkpoint periods was about 19% less than pre-checkpoint counts.     

Characterizing urban butterfly populations: the case for purposive point-count surveys

Developing effective butterfly monitoring strategies is key to understanding how butterflies interact with urban environments, and, in turn, to developing local conservation practices. We investigated two urban habitat types (public gardens and restored/reconstructed prairies) and compared three survey methods (Pollard transects, purposive point counts, and random point counts) to determine which was most productive for detecting butterflies and assessing family diversity. We conducted 66 butterfly surveys by using each method (198 total) from May through September in 2015 and 2016 at six sites (three public gardens and three prairies) in Ames, Ankeny and Des Moines, Iowa. All survey methods were used on 11 sampling dates at each site. Overall, we observed 2,227 butterflies representing 38 species: 1,076 in public gardens and 1,151 in prairie areas. We used a smaller data set standardized for survey effort, including 1,361 of these sightings, to compare survey methods and habitat types. Although there were no significant differences in number of butterfly sightings between the two habitats, more sightings (798) were documented by using purposive point counts when compared to Pollard transects (297) or random point counts (266) (for both comparisons, p?<?0.0001). Occupancy modeling also indicated that purposive point counts were most effective in detecting certain species of butterflies, most notably those within the Pieridae (whites, sulphurs) and Papilionidae (swallowtails). We conclude that public gardens and restored/reconstructed prairies in urban settings can provide important butterfly habitat, and that purposive point-count surveys are most effective for detecting butterflies in these relatively small-scale landscape features.

     

Reliability of normalisation methods for EMG analysis of neck muscles

Acceptable reliability of normalisation contractions in electromyography (EMG) is paramount for testing conducted over a number of days or if normal laboratory strength testing equipment is unavailable. This study examined the reliability of maximal voluntary isometric contractions (MVIC) and sub-maximal (60%) isometric contractions for use in neck muscle EMG studies. Surface EMG was recorded bilaterally from eight sites around the neck at C4/5 level from five healthy male subjects. Subjects performed MVIC and sub-maximal normalisation contractions using an isokinetic dynamometer (ID) and a portable cable dynamometer with attached strain gauge (PCD) in addition to a MVIC against a manual resistance (MR). Subjects were tested in flexion, extension, left and right lateral bending and were retested by the same tester within a two-week period. Intra class correlation co-efficients (ICC) were calculated for each testing method and contraction direction and a mean ICC was calculated across all contraction directions. All normalisation methods produced excellent within-day reliability (mean ICC >0.80) but only the MVICs using the ID and PCD had acceptable reliability when assessed between-days. This study confirmed the validity of using MVICs elicited using the ID and PCD as reliable reference contractions for the normalisation of neck EMG.     

A New Approach to Estimating Life Tables with Covariates and Constructing Interval Estimates of Life Table Quantities

Extant approaches to constructing life tables generally rely on the use of population data, and differences between groups defined by discrete characteristics are examined by disaggregating the data before estimation. When sample data are used, few researchers have attempted to include covariates directly in the process of estimation, and fewer still have attempted to construct interval estimates for state expectancies when covariates are used. In this paper, we present a Bayesian approach that is useful for producing interval estimates for single‐decrement, multiple‐decrement, and multistate life tables. The method involves (1) estimating a hazard or survival model using Bayesian Markov chain Monte Carlo (MCMC) methods to produce a sample from the posterior distribution for the parameters of the model; (2) generating distributions of transition probabilities for selected values of covariates using the sample of model parameters; (3) using these distributions of transition probabilities as inputs for life table construction; and (4) summarizing the distribution of life table quantities. We illustrate the method on data simulated from the Berkeley Mortality Database, data from the National Health and Nutrition Examination Survey (and follow‐ups), and data from the National Long Term Care Survey, and we show how the results can be used for hypothesis testing.     

Modeling Repeatable Events Using Discrete‐Time Data: Predicting Marital Dissolution

I join two methodologies by illustrating the application of multilevel modeling principles to hazard‐rate models with an emphasis on procedures for discrete‐time data that contain repeatable events. I demonstrate this application using data taken from the 1995 National Survey of Family Growth (NSFG) to ascertain the relationship between multiple covariates and risk of subsequent marital dissolution. I consider both fixed‐ and random‐effects versions of the multilevel model, as well as a Generalized Estimating Equation alternative to estimating random effects. I compare results obtained from the various estimators, noting why differences occur, and recommend when to choose the various alternatives. I also provide a set of SAS and STATA programs that can be used to analyze the NSFG data.     

The pattern of distribution and diversity of avifauna over an urbanizing tropical landscape

An investigation was done to determine the occurrence and composition of avian fauna community in the urbanizing city of Nairobi, Kenya. We conducted bird counts in sample sites randomly distributed over the Nairobi landscape within a two-year period. The proportion of seven different land cover types derived from within a 500 m radius of classified satellite image described the habitat condition of each sample site. Multivariate analysis of the site and species data indicated that savannah vegetation, forest and agriculture land cover types were the main environmental gradients that differentiated the sample sites. Four clusters of sample sites occurred on the ordination plane according to canonical correspondence analysis (CCA). From 50 families of birds observed, species related to bush and scrub habitats occurred at a rate of about 31 %, followed by grassland species at 20 % and forest species at about 16 % rate. Out of CCA, five functional groups of birds were distinguishable. The proportion of sites occupied by birds per functional group and mean count of individual birds declined significantly, p?<?0.0001, as groups of birds changed from being urban-related to savannah and then to forest-related species. One cluster comprised birds marked as having conservation concern status and related mainly to savannah vegetation of scrub and grasslands. In this landscape context, features such as native savannah vegetation and woodland accompanied by a process of controlled land use, could greatly mitigate negative impacts of ecosystem degradation on the sensitive tropical urban bird biodiversity.     

Implementations,change management and evaluation: A case study of the centre for excellence in teaching and learning in reusable learning objects

Abstract

This paper describes an e-learning project in the area of reusable learning objects (RLOs) that has attempted to bring about technological and cultural change across three diverse universities. The three partner universities in the Centre for Excellence in Teaching and Learning in Reusable Learning Objects (RLO-CETL) are London Metropolitan University (LMU), the Universities of Cambridge (CAM) and Nottingham (NOTT). The goal of our study was to gain an improved understanding of the following question: what are the cultural differences across three organisations in the management of people and change? The work described in this paper draws on an institutional change model and grounded theory to provide a framework for the qualitative analysis of data from practitioners from the three partner sites. A key facet of our change model is the notion of the tipping point; this is a point at which enough individuals in a system have adopted an innovation so that the innovation's further rate of adoption becomes self-sustaining. It appears that key pockets in some of the partner sites have hit the tipping point. Various other findings are presented on the basis of our qualitative analysis, which draw out the cultural differences across the three sites. The paper concludes by asserting that the qualitative analysis has raised various issues, which are worthy of further research, particularly the under-researched role of students as key change agents.     

Lentic and lotic odonate communities and the factors that influence them in urban versus rural landscapes

Habitat alteration via urbanization has very different effects on even closely related taxa. Most research investigating the ecological effects of urbanization has focused on birds or mammals, resulting in a relatively poor understanding of how the species richness and community composition of invertebrates may change. We quantified differences in species richness of adult odonates (dragonflies and damselflies) at lentic and lotic sites in urban and rural landscapes, and we examined environmental factors that might drive the differences in community composition that we observed. For lotic sites, species richness did not differ between urban versus rural sites for either dragonflies or damselflies. For lentic sites, urban and rural sites contained similar dragonfly species richness, but damselfly species richness was significantly lower at urban sites than at rural sites. Differences in lentic odonate community composition were associated with the amount of urban development within 150 m of each site, mean algal coverage, and distance to the urban center. At lotic sites, water temperature and distance to the urban center were correlated with differences in odonate community composition. The differing responses to urbanization observed in this study were probably a consequence of differences between lentic versus lotic ecosystems and between dragonflies versus damselflies in dispersal capability and habitat specificity. Given that different environmental factors affected these taxa differently in lentic and lotic sites, maintaining the highest level of odonate diversity possible across a landscape will require the use of different management practices for each ecosystem type.     

Random-effects models for analyzing clustered data from a nutrition education intervention

When evaluating the effects of public health intervention, larger units, or clusters, of individuals are often the unit of randomization and implementation. Ignoring dependency in the data due to clustering can misrepresent intervention effects. Random-effects models (REMs) may be a useful way to analyze such data. The present study compares results of analyses of data from a nutrition intervention program using four different methods: (a) usual multiple regression analysis using individual subject data, (b) usual multiple regression analysis using the classroom cluster as the unit of analysis, (c) two-level REM model with subjects clustered within classrooms, and (d) two-level REM model with subjects clustered within sites.     

Effects of off-road vehicles on reproductive success of pine snakes (<Emphasis Type="Italic">Pituophus melanoleucus</Emphasis>) in the New Jersey pinelands

Considerable attention has been devoted to the effects of people and their vehicles on birds and mammals, but possible effects on reptiles in populated areas have received less attention. Moreover, the effects of human activities on reptile reproductive success itself has been harder to demonstrate. This paper examines the effect of management of off-road vehicles in New Jersey’s pinelands on the reproductive success of pine snakes (Pituophus melanoleucus) from 1986 to 2005. We used the percentage of snakes in each hibernaculum that were young of the year (hatchlings) as an indicator of reproductive success, and compared this percent for five hibernacula that were in an area with varying degrees of off-road vehicle (ORV) disturbance, with 12 hibernacula in areas with no ORV disturbances (reference sites). This percent took into account differences in absolute numbers from one location to another, and over time due to hibernacula destruction (by people or predators) and natural variations (food supply). The ORV pressure in the pinelands is intense because it lies within the most densely populated urban area in the United States. Although the number of snakes in the reference hibernacula varied over the years from 46 to 63, the percent of young in these hibernacula did not vary significantly over the 20 year period (21–29%). In contrast, the percent-young in the disturbed sites differed significantly in years without ORV disturbance (28%) compared to those with ORV disturbance (15 and 16%, P < 0.01). Further, there were no differences between the percent of young in the reference sites and those in the disturbed site in years without ORV disturbance. ORV disturbance ceased only with the creation of large dirt berms coupled with fences that could not be easily broken. These data indicate the importance of having detailed population data on pine snakes in hibernacula, on ORV use (or indications of such use), and of managing ORV use to protect sensitive populations. Maintenance of healthy pine snake populations in urban areas may require continued adaptive management.     

Mover-Stayer Models for Analyzing Event Nonoccurrence and Event Timing With Time-Dependent Covariates: An Application to An Analysis of Remarriage

This paper introduces a novel extension of mover-stayer models for duration data that allows time-dependent covariates to be used for both a pair of regression equations, one that identifies the determinants of event timing and one that identifies the determinants of the probability of ultimate event nonoccurrence. Existing models intended to distinguish covariate effects on event timing from those on event nonoccurrence cannot use time-dependent covariates in the equation for the probability of ultimate event nonoccurrence. This paper applies the new model to an analysis of remarriage among American women. The analysis generally demonstrates that some covariates effect remarriage timing while others affect the probability of ultimate remarriage nonoccurrence. Some differences in patterns of remarriage between black women and white women are also reported. Theoretical implications of these findings are discussed.     

Self‐actualization and sexual permissiveness,satisfaction, prudishness,and drive among female undergraduates

The relationship between self‐actualization and aspects of female sexuality was examined. Ninety‐five white, single female undergraduates from a regional southeastern state university volunteered as subjects. Three questionnaires were administered: the Personal Orientation Inventory (POI), Eysenck's Inventory of Attitudes to Sex, and a two‐item religiosity measure. The data were analyzed via correlation and hierarchical multiple regression analysis which employed religiosity, age, major, grade, residence (on/off campus), and the order of test presentation as covariates. The results indicated that, when the effects of the covariates were controlled, there was a significant relationship between self‐actualization and sexual permissiveness, sexual satisfaction and prudishness. Although self‐actualization and sexual libido were significantly correlated, self‐actualization did not account for a significant portion of the variance in sexual libido after the effects of the covariates were controlled. Implications for future research include using different populations to investigate the relationship between self‐actualization and sexual attitudes and behaviors, using different measures of self‐actualization to investigate its relationship to sexual attitudes and behaviors, and examining the relationship between self‐actualization and other aspects of sexuality.     

An Evaluation of the Effectiveness of an FE/HE Partnership in the Delivery of a Preparation for Practice Module within an Undergraduate Social Work Degree Programme

The Preparation for Practice module at the University of Ulster is delivered to 170 first year students via a collaborative arrangement between higher and further education institutions. In each of the five sites, students receive large group and small group teaching facilitated by social work training agency workers and academic tutor dyads. An evaluation of the module sought the perceptions of the agency and academic facilitators regarding the overall collaborative arrangement and the model of co-teaching involving social work academics and agency partners. Respondents were asked to complete a semi-structured questionnaire, which generated data from a Likert scale and also invited qualitative commentary. The Likert scale data were analysed via SPSS and the qualitative information was scrutinised using a manual thematic analysis technique. Findings indicated that continuous communication, consistency in programme content and the acknowledgement of the differences in organisation resources were key to a successful collaborative arrangement. It was also noted that a co-teaching model should be viewed as a positive vehicle for achieving module objectives in a safe learning environment.     

Assessing manual lifting tasks based on segment angle interpolations

This study investigates the effects of the number of interpolation points on the prediction accuracy of segment angle trajectory during lifting. Ten participants performed various lifting tasks while a motion tracking system recorded their movements. Two-point through ten-point equal time-spaced segment angles extracted from major segment trajectory data captured by the motion tracking system were used to re-generate the whole body lifting motion by using polynomial and cubic spline interpolation methods. The root mean square error (RMSE) between the reference (motion tracking system) and the estimated (interpolation method) segment angle trajectories were calculated to quantify the prediction accuracy. The results showed that the cubic spline interpolation will yield a smaller RMSE value than one based on the polynomial interpolation. While increasing the number of interpolation points can reduce the RMSE of the estimated segment angle trajectories, there was a diminishing advantage in continuing to add interpolation points. A sensitivity analysis suggests that if the estimation of the segment angles at each interpolation point deviates considerably from the real value, and cannot be controlled at a low level (<10 (), the use of higher number of interpolation points will not improve the estimation accuracy.     

VARIANCE FUNCTION REGRESSIONS FOR STUDYING INEQUALITY

Regression-based studies of inequality model only between-group differences, yet often these differences are far exceeded by residual inequality. Residual inequality is usually attributed to measurement error or the influence of unobserved characteristics. We present a model, called  variance function regression , that includes covariates for both the mean and variance of a dependent variable. In this model, the residual variance is treated as a target for analysis. In analyses of inequality, the residual variance might be interpreted as measuring risk or insecurity. Variance function regressions are illustrated in an analysis of panel data on earnings among released prisoners in the National Longitudinal Survey of Youth. We extend the model to a decomposition analysis, relating the change in inequality to compositional changes in the population and changes in coefficients for the mean and variance. The decomposition is applied to the trend in U.S. earnings inequality among male workers, 1970 to 2005.     

Using modern methods for missing data analysis with the social relations model: A bridge to social network analysis

Social network analysis identifies social ties, and perceptual measures identify peer norms. The social relations model (SRM) can decompose interval-level perceptual measures among all dyads in a network into multiple person- and dyad-level components. This study demonstrates how to accommodate missing round-robin data using Bayesian data augmentation, including how to incorporate partially observed covariates as auxiliary correlates or as substantive predictors. We discuss how data augmentation opens the possibility to fit SRM to network ties (potentially without boundaries) rather than round-robin data. An illustrative application explores the relationship between sorority members’ self-reported body comparisons and perceptions of friends’ body talk.     

Medical students' exposure to formaldehyde in a gross anatomy dissection laboratory.

The authors studied 150 first-year medical students exposed to formaldehyde during the dissection of cadavers in a gross anatomy laboratory. As a reference group, they used 189 third- and fourth-year medical students matched for sex, ethnic group, and age. Environmental and personal samples were collected to determine the exposure to formaldehyde among the first-year students. The mean concentration of formaldehyde in parts per million (ppm) in the area was 0.50 ppm (range = 0.40-0.60 ppm) and the personal sample was 0.74 ppm (range = 0.41-1.20 ppm). No significant differences were noted in the pre- and post-exposure mean FEV1 (forced expiratory volume in 1 second) and FVC (forced vital capacity) among the 22 randomly selected exposed male and female subjects. Significant differences, however, were observed in the exposed group for symptoms of decreased ability to smell, eye irritation, throat irritation, and dry mouth in comparison with the reference group. These symptoms were also significantly related to the time and place of occurrence. Medical schools should take more concrete measures to reduce students' exposure to formaldehyde. Meanwhile, although it is not now the practice in most medical schools, students should have ready access to goggles and respirators when working in dissection laboratories.     

A randomized field trial in Oakland, California

This study evaluates the impact of a civil remedy program (Beat Health) on drug and disorder problems under experimental field trial conditions. Using calls for service data, the authors find statistically significant differences between the control and experimental groups, when drug problem calls prior to the start of the intervention were compared to drug calls during a 12-month follow-up period. The Beat Health sites, especially the residential sites, improved relative to the control sites. By contrast, the control treatment (patrol response) led to significant increases in drug problems, particularly at the commercial properties included in this study. The authors also examined the spatial influences of the Beat Health and patrol responses in catchment areas surrounding each of the 100 study sites. The results show some improvement in the experimental residential sites. The authors found, however, a possible displacement of drug problems in and around both the commercial experimental and control sites. They show that the displacement effect is most notable in the commercial control sites.