Median split, k-group split, and optimality in continuous populations

Continuous populations are grouped in many social, economic, medical, or technical fields of research. However, by grouping them, a lot of information provided by the continuous population is lost. Especially the median split, which is still adopted by many researchers, and its generalization to an equiprobable k-group split lead to a high efficiency loss. Here, this loss of information is investigated by analytical and numerical analyses for some typical symmetric and skew population distributions often found in applications. Various distribution parameters, numbers of groups, and split methods are taken from theoretical considerations and real data sets. Losses sometimes in excess of 50% can be reduced by optimal grouping.     

Evaluation of an inter-organizational program for prevention of work-related injuries in a WHO Safe Community

OBJECTIVE: To evaluate the effect of a community-based injury prevention program on work-related injuries. STUDY DESIGN: A population-based quasi-experimental design was used with pre- and post-implementation measurements in an intervention and a control area. The program was based on cross-sectoral participation in detecting and taking action against work-related injuries. Change in the relative risk of injury was estimated by the odds ratio. RESULTS: The relative risk of work-related injury decreased following program exposure, whereas a tendence toward increase was observed in the control area. Middle-aged men accounted for the largest decrease in injury risk. Among the women, a decrease was observed only in the upper middle-aged group. No female-dominated occupational area showed a decrease in injury risk following exposure to the program. CONCLUSION: The study showed that the community-based approach had a general effect on the incidence of work-related injuries.     

Kernel Estimation of the Spectral Density of Stationary Random Closed Sets

A non‐parametric kernel estimator of the spectral density of stationary random closed sets is studied. Conditions are derived under which this estimator is asymptotically unbiased and mean‐square consistent. For the planar Boolean model with isotropic compact and convex grains, an averaged version of the kernel estimator is compared with the theoretical spectral density.     

Some remarks on experimental design for estimating the expectation of a stationary random process

For estimation of the mean of a stationary random process the variance-optimal choice of the observation points (the so called experimental design) is considered. For this discrete and continuous designs are introduced, some known results of process statistics are interpreted to experimental design and a proposal for simplification of the minimization problem is offered, moreover it is proved, that for monotone decreasing eovarianee functions a design, for which the points near the ends of the observation interval are more dense than in the middle, is better than the equidistant design.     

Facial reactions in preschoolers: A descriptive study

The facial behavior during a marble rolling game was analyzed for two samples of children between the ages of 2 and 5 years using the Facial Action Coding System (FACS). In addition, for a subsample of children temperament ratings were available. Analysis of coding reliability showed that frequency as well as temporal location coding can be reliably performed for preschoolers. The facial movements show a frequency distribution which is highly similar in both samples. Movements of the mouth, especially the components of smiling, and some movements of the eye region, were observed frequently. Most other facial movements were infrequent events. The more often shown facial movements were stable over a period up to 18 months. In addition, sum-scores of emotion-relevant Action Units were meaningfully related to infant temperament characteristics.