Non-parametric Curve Estimation by Wavelet Thresholding with Locally Stationary Errors

An important aspect in the modelling of biological phenomena in living organisms, whether the measurements are of blood pressure, enzyme levels, biomechanical movements or heartbeats, etc., is time variation in the data. Thus, the recovery of a 'smooth' regression or trend function from noisy time-varying sampled data becomes a problem of particular interest. Here we use non-linear wavelet thresholding to estimate a regression or a trend function in the presence of additive noise which, in contrast to most existing models, does not need to be stationary. (Here, non-stationarity means that the spectral behaviour of the noise is allowed to change slowly over time). We develop a procedure to adapt existing threshold rules to such situations, e.g. that of a time-varying variance in the errors. Moreover, in the model of curve estimation for functions belonging to a Besov class with locally stationary errors, we derive a near-optimal rate for the -risk between the unknown function and our soft or hard threshold estimator, which holds in the general case of an error distribution with bounded cumulants. In the case of Gaussian errors, a lower bound on the asymptotic minimax rate in the wavelet coefficient domain is also obtained. Also it is argued that a stronger adaptivity result is possible by the use of a particular location and level dependent threshold obtained by minimizing Stein's unbiased estimate of the risk. In this respect, our work generalizes previous results, which cover the situation of correlated, but stationary errors. A natural application of our approach is the estimation of the trend function of non-stationary time series under the model of local stationarity. The method is illustrated on both an interesting simulated example and a biostatistical data-set, measurements of sheep luteinizing hormone, which exhibits a clear non-stationarity in its variance.     

Exploring user experience and technology acceptance for a fall prevention system: results from a randomized clinical trial and a living lab

Background

Falls are common in older adults and can result in serious injuries. Due to demographic changes, falls and related healthcare costs are likely to increase over the next years. Participation and motivation of older adults in fall prevention measures remain a challenge. The iStoppFalls project developed an information and communication technology (ICT)-based system for older adults to use at home in order to reduce common fall risk factors such as impaired balance and muscle weakness. The system aims at increasing older adults’ motivation to participate in ICT-based fall prevention measures. This article reports on usability, user-experience and user-acceptance aspects affecting the use of the iStoppFalls system by older adults.

Methods

In the course of a 16-week international multicenter study, 153 community-dwelling older adults aged 65+ participated in the iStoppFalls randomized controlled trial, of which half used the system in their home to exercise and assess their risk of falling. During the study, 60 participants completed questionnaires regarding the usability, user experience and user acceptance of the iStoppFalls system. Usability was measured with the System Usability Scale (SUS). For user experience the Physical Activity Enjoyment Scale (PACES) was applied. User acceptance was assessed with the Dynamic Acceptance Model for the Re-evaluation of Technologies (DART). To collect more detailed data on usability, user experience and user acceptance, additional qualitative interviews and observations were conducted with participants.

Results

Participants evaluated the usability of the system with an overall score of 62 (Standard Deviation, SD 15.58) out of 100, which suggests good usability. Most users enjoyed the iStoppFalls games and assessments, as shown by the overall PACES score of 31 (SD 8.03). With a score of 0.87 (SD 0.26), user acceptance results showed that participants accepted the iStoppFalls system for use in their own home. Interview data suggested that certain factors such as motivation, complexity or graphical design were different for gender and age.

Conclusions

The results suggest that the iStoppFalls system has good usability, user experience and user acceptance. It will be important to take these along with factors such as motivation, gender and age into consideration when designing and further developing ICT-based fall prevention systems.

     

Interpretation of the four types of analysis of variance tables in sas

Various computational methods exist for generating sums of squares in an analysis of variance table. When the ANOVA design is balanced, most of these computational methods will produce equivalent sums of squares for testing the significance of the ANOVA model parameters. However, when the design is unbalanced, as is frequently the case in practice, these sums of squares depend on the computational method used.- The basic reason for the difference in these sums of squares is that different hypotheses are being tested. The purpose of this paper is to describe these hypotheses in terms of population or cell means. A numerical example is given for the two factor model with interaction. The hypotheses that are tested by the four computational methods of the SAS general linear model procedure are specified.

Although the ultimate choice of hypotheses should be made by the researcher before conducting the experiment, this paper

PENDLETON,VON TRESS,AND BREMER

presents the following guidelines in selecting these hypotheses:

When the design is balanced, all of the SAS procedures will agree.

In unbalanced ANOVA designs when there are no missing cells. SAS Type III should be used. SAS Type III tests an unweighted hypothesis about cell means. SAS Types I and II test hypotheses that are functions of the ceil frequencies. These frequencies are often merely arti¬facts of the experimental process and not reflective of any underlying frequencies in the population.

When there are missing cells, i.e. no observations for some factor level combinations. Type IV should be used with caution. SAS Type IV tests hypotheses which depend     

Effort-reward imbalance,overcommitment and sleep in a working population

The relationship between workplace characteristics and nocturnal sleep in a working population was investigated. Data from 709 employees (mean age=39 years; 87% men) from two German companies were analysed at the entry of the longitudinal cohort study (overall accrual 73%). We investigated the association between the effort-reward imbalance model at work (Siegrist, ) and self-reported sleep quality and sleep disturbances, as assessed by the Jenkins Sleep Quality Index. Effort and overcommitment were found to be higher, and reward was lower in participants with lower (N=328) vs. higher sleep quality (N=381), as well as in participants with (N=217) vs. without (N=492) disturbed sleep (all ps<.001). In regression analyses, lower sleep quality (R ²=.33) and sleep disturbances (R ² _Nagelkerke=.33) were predicted by older age, female gender (only significant for sleep disturbances), shift-work, lower physical and mental health functioning, and higher overcommitment. Individuals were 1.7 times more likely to report disturbed sleep per standard deviation increase in overcommitment. Gender-stratified analyses revealed that higher overcommitment was associated with unfavourable sleep in men, while in women poor sleep was related to lower reward. The findings suggest that overcommitment at work interferes with restful sleep in men, while in women disturbed sleep may be associated with the amount of overcommitment and perceived job reward and sleep quality associated with the perceived reward.     

A necessary dialogue: a South African case study exploring the role of national HRD in HIV/AIDS non-government organizations

This article makes the case for a coordinated and multi-faceted national level response to the HIV/AIDS crisis in South Africa from the field of human resource development (HRD), arguing that national policy debate on this issue must include the development of human resources in HIV/AIDS non-governmental organizations (NGOs). An exploration of potential connections between HIV/AIDS and HRD was conducted with a qualitative case study in Port Elizabeth, South Africa. Through this study, four major thematic categories emerged in connection to the work of NGOs involved in the management of HIV/AIDS, government policy, and the emerging theory and practice of national human resource development (NHRD). In addition, findings pointed to the need for HRD research to be conducted in HIV/AIDS related NGOs given their front-line roles in both policy and practice. Initial suggestions for dialogue between NGOs involved with managing HIV/AIDS and the HRD research and practice community are made along with recommendations for stronger linkages between NHRD and HIV/AIDs.     

Configural Frequency Analysis: the Search for Extreme Cells

Configural Frequency Analysis (CFA) asks whether a cell in a cross-classification contains more or fewer cases than expected with respect to some base model. This base model is specified such that cells with more cases than expected (also called types) can be interpreted from a substantive perspective. The same applies to cells with fewer cases than expected (antitypes). This article gives an introduction to both frequentist and Bayesian approaches to CFA. Specification of base models, testing, and protection are discussed. In an example, Prediction CFA and two-sample CFA are illustrated. The discussion focuses on the differences between CFA and modelling.     

The ‘New Minimalist Approach’ to Private‐Sector Development: A Critical Assessment

Recent literature on private‐sector development emphasises the need to establish a ‘level playing field’ and tends to disregard selective supportive interventions. The most commonly highlighted elements are administrative simplification and effective property rights policies, with business services largely left to private providers ‐ what we call the ‘new minimalist approach’ (NMA). However, the NMA is based on certain unrealistic assumptions and is barely backed by empirical evidence. A range of complementary public policies is needed to create competitive sectors and overcome internal constraints, especially in small‐scale economies.     

Characteristics of Women with Body Size Satisfaction at Midlife: Results of the Gender and Body Image (GABI) Study

This study characterizes the profile of women (N?=?1,789) ages 50 and over who report body size satisfaction on a figure rating scale. Satisfied women (12.2%) had a lower body mass index and reported fewer eating disorder symptoms, dieting behaviors, and weight and appearance dissatisfaction. Interestingly, satisfied women exercised more than dissatisfied women, and weight and shape still played a primary role in their self-evaluation. Weight monitoring and appearance-altering behaviors did not differ between groups. Body satisfaction was associated with better overall functioning. This end point appears to represent effortful body satisfaction rather than passive contentment.     

Mexican Migration Networks in the United States, 1980–20001

Between 1980 and 2000, about 1.2 million Mexican immigrants settled in 47 new settlement states. In the past, these immigrants would have settled in California, Texas, or Illinois, the three traditional states for Mexican settlement. Explaining this dispersion, the network saturation theory claims that high‐volume migration of Mexicans finally saturated the housing and job opportunities of Mexicans in traditional states and especially in Los Angeles. High rents and low wages then encouraged Mexican immigrants to select new states for settlement. This article subjects the network saturation theory to a rigorous reanalysis using new evidence. The empirical results tend to confirm the network saturation theory.