The accuracy of normal approximation in a heterogeneous panel data unit root test

Tests for unit roots in panel data have become very popular. Two attractive features of panel data unit root tests are the increased power compared to time-series tests, and the often well-behaved limiting distributions of the tests. In this paper we apply Monte Carlo simulations to investigate how well the normal approximation works for a heterogeneous panel data unit root test when there are only a few cross sections in the sample. We find that the normal approximation, which should be valid for large numbers of cross-sectional units, works well, at conventional significance levels, even when the number of cross sections is as small as two. This finding is valuable for the applied researcher since critical values will be easy to obtain and p-values will be readily available.     

A Qualitative Analysis of Strengths and Vulnerabilities in Sexually Assaulted Women

Clinicians and researchers alike have pointed to the considerable variation in trauma responses among women who have been raped. This qualitative study attempts to enhance the understanding of strengths and vulnerabilities in women who have been sexually assaulted and factors which influence their recovery. The results of the study suggest that there is an association between a woman's post-traumatic stress response to rape and her pre-existing perceptions of self and other. Women with positive early life experiences were able to mobilize adaptive coping mechanisms and thereby diminish the long-term impact of the sexual assault experience. In contrast, women with disruptive or traumatic early life experiences appeared to have negative views of self and other reinforced, which subsequently interfered with their ability to activate adaptive coping mechanisms. Implications of these findings for the development of treatment programs are discussed.     

Long-term Stability of Social Participation

The long-term stability of social participation was investigated in a representative urban population of 415 men and 579 women who had taken part in the nationwide Mini-Finland Health Survey in the years 1978–1980 and were re-examined 20 years later. Stability was assessed by means of the following tracking coefficients: kappa, proportion of stability, Spearman correlation, and stability coefficient (odds ratio) for engagement in clubs and voluntary societies, cultural and sports attendance, congregational activity, outdoor and productive activity, cultural interests, and hobby activity. The tracking results showed fair to moderate stability for the above measures of social participation, varying from the highest weighted kappa (0.43) for congregational activity in women to the lowest weighted kappa (0.22) for cultural and sports attendance in men. Migration from rural to urban community did not affect the stability of social participation. The underlying latent construct ‘social participation’ based on a two-wave multi-variable model showed good stability (r = 0.65). We conclude that social participation rests on a fairly stable foundation making it a useful tool for long-term epidemiological studies.     

Entropy of unequal probability sampling designs

There exist many designs for unequal probability sampling. In this paper entropy, which is a measure of randomness, is used to compare eight designs. Both old and commonly used designs and more recent designs are included. Several different and general estimates of entropy are presented. In the quest of finding entropy, expressions for the probability function are derived for different designs. One of them is a recent general design called correlated Poisson sampling. Several designs are close to having maximum entropy, which means that the designs are robust. A few designs yield low entropy and should therefore in general be avoided.     

Early Theory of Mind Competencies: Do Infants Understand Others’ Beliefs?

Recent studies suggest that even infants attend to others’ beliefs in order to make sense of their behavior. To warrant the assumption of early belief understanding, corresponding competences need to be demonstrated in a variety of different belief‐inducing situations. The present study provides corresponding evidence, using a completely nonverbal object‐transfer task based on the general violation‐of‐expectation paradigm. A total of n = 36 infants (15‐month‐olds) participated in one of three conditions. Infants saw an actor who either observed an object’s location change, did not observe it, or performed the location change manually without seeing it (i.e., variations in the actor’s information access). Results are in accordance with the assumption that 15‐month‐old infants master different belief‐inducing situations in a highly flexible way, accepting visual as well as manual information access as a proper basis for belief induction.     

Mobilisierung, Staat und Demokratie

The explanation of the emergence and consolidation of democratic regimes is one of the most important topics of political sociology. The main theoretical approaches can be divided into actor- and elite-theories on the one hand and structure- and modernization-theories on the other. This article combines actor- and structure-centered theories following the discussion of Lipset’s thesis of the connection between socio-economic modernization and democracy. Its theoretical starting point is the assertion that the emergence and consolidation of democratic regimes can be explained with reference to the power resources and interests of collective actors. These are determined in two ways by structural conditions: first, the social structural basis for the mobilization of collective actors changes with socio-economic modernization processes. Second, the mobilization of actors is dependent on certain conditions, which are influenced by modernization processes. The role of the state is emphasized, because the state can strongly affect the conditions of mobilization for collective actors in the civil society, and therefore block processes of democratization. The interests and power resources of state elites are not only conditioned by endogenous modernization processes, but furthermore by exogenous, geopolitical conditions. Therefore, the final result is, that socioeconomic modernization processes are a necessary but not sufficient condition for democratization.     

Investigation about a screening step in model selection

In many studies a large number of variables is measured and the identification of relevant variables influencing an outcome is an important task. For variable selection several procedures are available. However, focusing on one model only neglects that there usually exist other equally appropriate models. Bayesian or frequentist model averaging approaches have been proposed to improve the development of a predictor. With a larger number of variables (say more than ten variables) the resulting class of models can be very large. For Bayesian model averaging Occam’s window is a popular approach to reduce the model space. As this approach may not eliminate any variables, a variable screening step was proposed for a frequentist model averaging procedure. Based on the results of selected models in bootstrap samples, variables are eliminated before deriving a model averaging predictor. As a simple alternative screening procedure backward elimination can be used. Through two examples and by means of simulation we investigate some properties of the screening step. In the simulation study we consider situations with fifteen and 25 variables, respectively, of which seven have an influence on the outcome. With the screening step most of the uninfluential variables will be eliminated, but also some variables with a weak effect. Variable screening leads to more applicable models without eliminating models, which are more strongly supported by the data. Furthermore, we give recommendations for important parameters of the screening step.