Walkability of local communities: using geographic information systems to objectively assess relevant environmental attributes.

Geographic Information Systems (GIS) can be used to objectively measure features of the built environment that may influence adults’ physical activity, which is an important determinant of chronic disease. We describe how a previously developed index of walkability was operationalised in an Australian context, using available spatial data. The index was used to generate a stratified sampling frame for the selection of households from 32 communities for the PLACE (Physical Activity in Localities and Community Environments) study. GIS data have the potential to be used to construct measures of environmental attributes and to develop indices of walkability for cities, regions or local communities.

Recreational facilities and leisure-time physical activity : an analysis of moderators and self-efficacy as a mediator

Objective: To examine socio-demographic and psychosocial moderators, and self-efficacy as a mediator of the cross-sectional relationships between having access to recreational facilities and leisure-time physical activity (LTPA); to investigate the extent to which the environment-LTPA associations could be explained by self-selection to neighborhoods.

Design: A two-stage stratified sampling design was used to recruit 2,650 adults (aged 20-65) from 32 urban communities varying in walkability and socioeconomic status. Participants reported perceived access to facilities and home equipment for LTPA, weekly minutes of LTPA, self-efficacy for and enjoyment of LTPA, reasons for neighborhood selection, and socio-demographic characteristics.

Main Outcome Measures: Self-reported recreational walking and other forms of moderate-to-vigorous LTPA expressed in MET-minutes.

Results: Specific types of recreational facilities were independently  associated with LTPA. Age, education, being overweight/ obese, reasons for neighborhood selection, enjoyment of, and self-efficacy for LTPA moderated these relationships. Self-efficacy was not a significant mediator of these cross-sectional associations.

Conclusion: These findings have potentially significant implications for the planning of environmental interventions aimed at increasing population-level LTPA particularly in those who are less attitudinally inclined to being physically active.

How socio-economic status contributes to participation in leisure-time physical activity

The aim of this cross-sectional study was to identify individual, social, and environmental contributors (mediators) to individual- and area-level differences in leisure-time physical activity across socio-economic groups. A two-stage stratified sampling design was used to recruit 20–65 year old adults (N = 2194) living in 154 census collection districts of Adelaide, Australia (overall response rate: 12%). Participants completed two surveys six months apart (response rate on the second survey: 83%). Individual-level socio-economic status (SES) was assessed using self-report measures on educational attainment, household income, and household size. Area-level SES was assessed using census data on median household income and household size for each selected census district. Bootstrap generalized linear models were used to examine associations between SES, potential mediators, and leisure-time physical activity. The product-of-coefficient test was used to estimate mediating effects. All SES measures were independently associated with potential individual and social mediators of the SES-activity relationships. Individual- and area-level income was also associated with perceived neighborhood attributes. Self-efficacy and social support for physical activity explained virtually all of the differences in physical activity across educational attainment groups. Physical barriers to walking and access to public open space contributed in part to the explanation of differences in recreational walking across income groups. Yet, self-efficacy and social support were the key mediators of the observed relationships between individual- and area-level income and physical activity. This study suggests that in order to increase physical activity participation in the more disadvantaged segments of the population, comprehensive, multilevel interventions targeting activity-related attitudes and skills as well as social and physical environments are needed.

Physical environmental conditions, spawning and early-life stages of an estuarine fish : climate change implications for recruitment in intermittently open estuaries

Significant variation in the egg and larval survival and juvenile recruitment of estuarine fishes has been linked to fluctuating environmental conditions. This present study compared the distribution and abundance of black bream (Acanthopagrus butcheri) eggs and yolk-sac larvae between two microtidal estuaries of different flow regimes, where the riverine flow into the Glenelg estuary was around eight times the flow volume into the Hopkins estuary. Samples were collected monthly from September to November at sites along each estuary where vertical profiles of temperature, salinity and dissolved oxygen (DO) were measured, and vertically stratified sampling of black bream eggs and yolk-sac larvae was conducted using a Schindler sampler. Salt wedge formation was apparent in both estuaries, with significant de-oxygenation of deeper, saline waters. Eggs occurred in a wide range of DO levels but yolk-sac larvae were less common at the lowest levels. Most eggs and yolk-sac larvae were collected in salinities greater than 10. Results suggested that egg mortality was higher in the Hopkins than the Glenelg estuary, which may be associated with the hypoxic conditions characteristic of low-flow conditions. The results have significant implications in terms of climate change that is predicted to lead to warmer, drier conditions in south-eastern Australia, potentially increasing stratification and subsequent hypoxic zones.

Optimizing survey effort for burrow-nesting seabirds

Regular monitoring of seabird populations is necessary to improve our understanding of their responses to environmental change and inform conservation management. However, given the difficulty in accessing remote breeding sites and the limited resources typically available to land managers, conducting regular, extensive surveys of seabird populations is often not feasible. Our objective was to determine the minimum survey effort required to obtain accurate and precise population estimates of Short-tailed Shearwaters (Ardenna tenuirostris) and Little Penguins (Eudyptula minor), two abundant burrowing seabird species in southeastern Australia, by comparing bootstrapped means and confidence intervals under different sampling regimes on four islands. We found that, in many cases, survey effort (the proportion of transects and quadrats along transects surveyed) could be reduced. For Short-tailed Shearwaters, reducing the number of transects resulted in a maximum difference of 15% between the means at full survey effort and two levels of reduced survey effort. Means differed by <3% when we halved the number of quadrats. For Little Penguins, reducing the number of transects and quadrats by 50% resulted in differences of 7-40% and 4-34%, respectively, between the full and reduced survey effort means. Confidence intervals generally increased with decreasing survey effort for both species. Differences in required survey effort between the two species in our study may have been due to differences in burrow distribution on islands, with Short-tailed Shearwater burrows generally uniformly distributed on each island and Little Penguin burrows typically occurring in patches. These would be influenced by island-specific characteristics in concert with habitat preferences, population size, and seasonal variation in seabird abundance. Stratified sampling did not increase survey accuracy and simulations showed that large reductions in survey effort could be made under a pseudo-random sampling regime, with mean abundance estimates similar at most levels of survey effort. For both species, reducing the proportion of pseudo-random quadrats to 50% and 25% of the full survey effort produced confidence intervals of 12% and 21%, respectively, of the maximum, whereas a survey effort of 10% produced confidence intervals of up to 36% of the maximum for both species. A pseudo-random sampling regime would maximize survey efficiency because considerably fewer quadrats would be required and allow development of more efficient sampling protocols and regimes.

Ageing in an ultra-dense metropolis: perceived neighbourhood characteristics and utilitarian walking in Hong Kong elders

Objective
The neighbourhood built environment may affect walking behaviour of elders. However, such effects remain underexplored, especially in an Asian context. We examined associations of perceived environmental attributes with overall and neighbourhood-specific walking for transport in a sample of Chinese elders residing in Hong Kong, an ultra-dense Chinese metropolis.

Design
Cross-sectional observational study using a two-stage stratified sampling strategy.

Setting
Hong Kong, China.

Subjects
Chinese-speaking elders (n 484), with no cognitive impairment and able to walk without assistance, residing in thirty-two selected communities stratified by socio-economic status and walkability, were interviewer-administered validated measures of perceived neighbourhood environment and walking for transport.

Results
Much higher levels of transport-related walking (mean 569 (sd 452) min/week) than found in Western samples were reported. The degree of perceived access to shops, crowdedness, presence of sitting facilities and easy access of residential entrance were independently positively related to both frequency of overall and within-neighbourhood walking for transportation. Infrastructure for walking and access to public transport were predictive of higher frequency of transport-related walking irrespective of location, while the perceived degree of land-use mix was predictive of higher levels of within-neighbourhood walking.

Conclusions
The provision of easy access to shops, residential entrances and sitting facilities in the neighbourhood may promote overall transport-related walking, while a good public transport network and pedestrian infrastructure linking destination-poor with destination-rich locations may compensate for the detrimental effects of living in less walkable neighbourhoods. Governmental investment in these micro- and macro-environmental features would help the promotion of an active lifestyle in elders.

Outcropping reef ledges drive patterns of epibenthic assemblage diversity on cross-shelf habitats

Seafloor habitats on continental shelf margins are increasingly being the subject of worldwide conservation efforts to protect them from human activities due to their biological and economic value. Quantitative data on the epibenthic taxa which contributes to the biodiversity value of these continental shelf margins is vital for the effectiveness of these efforts, especially at the spatial resolution required to effectively manage theseecosystems. We quantified the diversity of morphotype classes on an outcropping reef system characteristic of the continental shelf margin in the Flinders Commonwealth Marine Reserve, southeastern Australia. The system is uniquely characterized by long linear outcropping ledge features in sedimentary bedrock that differ markedly from the surrounding low-profile, sand-inundated reefs. We characterize a reef system harboring rich morphotype classes, with a total of 55 morphotype classes identified from the still images captured by an autonomous underwater vehicle. The morphotype class Cnidaria/Bryzoa/Hydroid matrix dominated the assemblages recorded. Both a and b diversitydeclined sharply with distance from nearest outcropping reef ledge feature. Patterns of the morphotype classes were characterized by (1) morphotype turnover at scales of 5 to 10s m from nearest outcropping reef ledge feature, (2) 30 % of morphotype classes were recordedonly once (i.e. singletons), and (3) generally low levels of abundance (proportion cover) of the component morphotype class. This suggests that the assemblages in this region contain a considerable number of locally rare morphotype classes. This study highlights the particular importance of outcropping reef ledge features in this region, as they provide a refuge against sediment scouring and inundation common on the low profile reef that characterizes this region. As outcropping reef features, they represent a small fraction of overall reef habitat yet contain much of the epibenthic faunal diversity. This study has relevance to conservation planning for continental shelf habitats, as protecting a single, or few, areas of reef is unlikely to accurately represent the geomorphic diversity of cross-shelf habitats and the morphotype diversity that is associated with these features. Equally, whendesigning monitoring programs these spatially-discrete, but biologically rich outcropping reef ledge features should be considered as distinct components in stratified sampling designs.

Attending to risk in sequential sampling plans

Researchers typically tackle questions by constructing powerful, highlyreplicated sampling protocols or experimental designs. Such approaches often demand large samples sizes and are usually only conducted on a once-off basis. In contrast, many industries need to continually monitor phenomena such as equipment reliability, water quality, or the abundance of a pest. In such instances, costs and time inherent in sampling preclude the use of highlyintensive methods. Ideally, one wants to collect the absolute minimum number of samples needed to make an appropriate decision. Sequential sampling, wherein the sample size is a function of the results of the sampling process itself, offers a practicable solution. But smaller sample sizes equate to less knowledge about the population, and thus an increased risk of making an incorrect management decision. There are various statistical techniques to account for and measure risk in sequential sampling plans. We illustrate these methods and assess them using examples relating to the management of arthropod pests in commercial crops, but they can be applied to any situation where sequential sampling is used.

Selected Ranked Set Sampling

This paper proposes a sampling procedure called selected ranked set sampling (SRSS), in which only selected observations from a ranked set sample (RSS) are measured. This paper describes the optimal linear estimation of location and scale parameters based on SRSS, and for some distributions it presents the required tables for optimal selections. For these distributions, the optimal SRSS estimators are compared with the other popular simple random sample (SRS) and RSS estimators. In every situation the estimators based on SRSS are found advantageous at least in some respect, compared to those obtained from SRS or RSS. The SRSS method with errors in ranking is also described. The relative precision of the estimator of the population mean is investigated for different degrees of correlations between the actual and erroneous ranking. The paper reports the minimum value of the correlation coefficient between the actual and the erroneous ranking required for achieving better precision with respect to the usual SRS estimator and with respect to the RSS estimator.

Obesity and undernutrition in sub-Saharan African immigrant and refugee children in Victoria, Australia

The study assessed the anthropometric status of 337 sub-Saharan African children aged between 3-12 years who migrated to Australia. These children were selected using a snowball sampling method stratified by age, gender and region of origin. The prevalence rates for overweight and obesity were 18.4% (95%CI: 14 - 23%) and 8.6% (95%CI: 6% -12%) respectively. The prevalence rates for the indicators of undernutrition were: wasting 4.3% (95%CI: 1.6%-9.1%), underweight 1.2% (95%CI: 0.3%-3.0%), and stunting 0.3 (95%CI: 0.0%-1.6%). Higher prevalence of overweight/obesity was associated with lower household income level, fewer siblings, lower birth weight, western African background, and single parent households (after controlling for demographic and socio-economic factors). Higher prevalence rates for underweight and wasting were associated with lower household income and shorter lengths of stay in Australia respectively. No effect was found for child's age, gender, parental education and occupation for both obesity and undernutrition indices. In conclusion, obesity and overweight are very prevalent in SSA migrant children and undernutrition, especially wasting, was also not uncommon in this target group.

The health and well-being of adolescents: a school-based population study of the self-report child health questionnaire

Purpose: To evaluate a new generic measure of adolescent health status, the self-report version of the Child Health Questionnaire (CHQ), and provide population-based data. Furthermore, we aimed to examine the impact of common adolescent illness and health concerns on their health and well-being.

Methods: A stratified, two-stage, random cluster sampling design was used to obtain a cross-sectional sample of subjects through schools. A written questionnaire included the 80-item 12-scale self-report CHQ and items measuring health concerns, illnesses/health conditions, and sociodemographics.

Results: A total of 2361 adolescents participated (response rate of 70%). Reliability was high: Tests of internal consistency and discriminant validity reported 90% of item-scale correlations >.4; all scales had Cronbach alpha coefficients >.7. Adolescents with illnesses/conditions or health concerns reported lower scores and larger differences for content-related scales, supporting content and construct validity. Statistically significant age and gender trends were observed for Mental Health, Self-Esteem, General Health, and Family Cohesion scales. Health status worsened as health concerns increased (X2 linear trend, p = .00) with deterioration in health of 5–20% on all scales for emotional health concerns (40% of sample).

Conclusions: The self-report CHQ is a reliable and seemingly valid measure of health and well-being for adolescent health research, although additional measures may be required where scales have high ceiling values. The significantly lower scores reported by adolescents with illness and/or health concerns lend support to the use of standardized health measures and longitudinal research to further examine the impact of adolescent comorbidities and their causal determinants.

Reaching the invisible : overcoming sampling barriers in GLB research via web surveys

Sampling is fundamental to the credibility of any empirical investigation, and this is no different for the area of Gay, Lesbian and Bisexual (GLB) research. In fact, it would not be an overstatement to say that publication of GLB research into high quality and mainstream journals has been limited in part because of sampling issues. The purpose of this paper is to raise awareness of the unique sampling problems posed by GLB resaerch and to offer solutions to these through the use of web surveys and recruitment strategies. In particular, we provide data which show that, contrary to voiced concerns, when employed with a rigorous recruitment strategy, web surveys increase rather than reduce sampling coverage. Further, we provide evidence that the web survey technique can yield data of comparable quality to that obtained with a hard-copy survey. The paper concludes with strategies researchers can adopt to overcome barriers in obtaining a diverse GLB sample.

Applying GIS in physical activity research: community walkability and walking behaviours.

Physical activity provides many health benefits, including reduced risk of cardiovascular disease, Type II diabetes and some cancers. Environmental exposure factors (e.g., the built environment) are now receiving ever-increasing attention. Large-scale interdisciplinary studies on the association between attributes of local community environments and residents’ physical activity are being conducted. We will focus on findings from Australia - the Physical Activity in Localities and Community Environments (PLACE) study. PLACE is examining factors that may influence the prevalence and the social and spatial distribution of walking for transport and walking for recreation. A stratified two-stage cluster sampling strategy was used to select 32 urban communities (154 census collection districts), classified as high and low ‘walkable’ using a GISbased walkability index (dwelling density, intersection density, net retail area and land use mix) and matched for socio-economic status. We report data on a sub-sample of 1,216 residents who provided information on the perceived attributes of their community environments (e.g., dwelling density, access to services, street connectivity) and weekly minutes of walking for transport and for recreation. Moderate to strong associations were found between GIS indicators of walkability and the corresponding self-report measures. The walkability index explained the same amount of neighborhood-level variance in walking for transport as did the complete set of self-report measures. No significant associations were found with walking for recreation. Relevant GIS-based indices of walkability, for purposes other than transport need to be   developed.

What have sampling and data collection got to do with good qualitative research?

Objective: To highlight the importance of sampling and data collection  processes in qualitative interview studies, and to discuss the contribution of  these processes to determining the strength of the evidence generated and  thereby to decisions for public health practice and policy.

Approach: This discussion is informed by a hierarchy-of-evidence-for-practice  model. The paper provides succinct guidelines for key sampling and data  collection considerations in qualitative research involving interview studies. The  importance of allowing time for immersion in a given community to become  familiar with the context and population is discussed, as well as the practical  constraints that sometimes operate against this stage. The role of theory in  guiding sample selection is discussed both in terms of identifying likely sources  of rich data and in understanding the issues emerging from the data. It is noted  that sampling further assists in confirming the developing evidence and also  illuminates data that does not seem to fit. The importance of reporting sampling  and data collection processes is highlighted clearly to enable others to assess  both the strength of the evidence and the broader applications of the findings.

Conclusion: Sampling and data collection processes are critical to determining  the quality of a study and the generalisability of the findings. We argue that  these processes should operate within the parameters of the research goal, be  guided by emerging theoretical considerations, cover a range of relevant   participant perspectives, and be clearly outlined in research reports with an  explanation of any research limitations.

An empirical evaluation of sampling controversies in ratio-based modelling of corporate collapse

Empirical investigations regarding ratio-based modelling of corporate collapse have been on going for decades. With any study of an empirical nature, a data sample is a necessary prerequisite. It allows testing the performance of the prediction model, thereby establishing its practical relevance. However, it is necessary to first ensure that the data sample used satisfies certain conditions, and these have lead to some choice controversies. This paper considers the controversial issues that arise in data sampling, provides a critical evaluation of these issues, and makes choice recommendations on the controversial aspects, by empirically examining the literature.