A comparison of test statistics for the recovery of rapid growth‐based enumeration tests

This paper considers five test statistics for comparing the recovery of a rapid growth‐based enumeration test with respect to the compendial microbiological method using a specific nonserial dilution experiment. The finite sample distributions of these test statistics are unknown, because they are functions of correlated count data. A simulation study is conducted to investigate the type I and type II error rates. For a balanced experimental design, the likelihood ratio test and the main effects analysis of variance (ANOVA) test for microbiological methods demonstrated nominal values for the type I error rate and provided the highest power compared with a test on weighted averages and two other ANOVA tests. The likelihood ratio test is preferred because it can also be used for unbalanced designs. It is demonstrated that an increase in power can only be achieved by an increase in the spiked number of organisms used in the experiment. The power is surprisingly not affected by the number of dilutions or the number of test samples. A real case study is provided to illustrate the theory. Copyright © 2013 John Wiley & Sons, Ltd.     

Context Matters: Explaining How and Why Mobilizing Context Influences Motivational Dynamics

The emphasis in the social-psychological collective action literature is on why individuals take part in collective action; however, it does not elaborate on how different mobilizing contexts may appeal to distinct motivational dynamics to participate. The present study connects the microlevel of motivational dynamics of individual protesters with the mesolevel of social movement characteristics. To do so a field study was conducted. Protesters were surveyed in the act of protesting in two different demonstrations in two different town squares simultaneously organized by two social movements at exactly the same time against the same budget cuts proposed by the same government. But with one fundamental difference, the movements emphasized different aspects of the policies proposed by the government. This most similar systems design created a unique natural experiment, which enabled the authors to examine whether the motivational dynamics of individual protesters are moderated by the social movement context. Previous research suggested an instrumental path to collective action, and the authors added an ideology path. The authors expected and found that power-oriented collective action appeals to instrumental motives and efficacy and that value-oriented collective action appeals to ideological motives, and, finally, that efficacy mediates on instrumental motives and motivational strength, but only so in power-oriented action.     

Birds of a Feather? The Effect of Organizational Value Congruence on the Relationship Between Ministries and Quangos

In this paper we investigate differences between the organizational values of ministries and semi-autonomous executive agencies (quangos) that operate at arms’ length. Quangos are expected to operate more business-like, hence they can be expected to value profitability and other NPM-related values higher than ministries. Value incongruence between quangos and ministries is hypothesized to decrease their level of trust. These hypotheses are tested, using combined data from two Dutch surveys (n = 324). The results confirm the expectations, although different types of quangos have different degrees of value (in)congruence, which may lead to variations in the quality of the relationship with their parent ministry.     

Inference in Targeted Group‐Sequential Covariate‐Adjusted Randomized Clinical Trials

This article is devoted to the construction and asymptotic study of adaptive, group‐sequential, covariate‐adjusted randomized clinical trials analysed through the prism of the semiparametric methodology of targeted maximum likelihood estimation. We show how to build, as the data accrue group‐sequentially, a sampling design that targets a user‐supplied optimal covariate‐adjusted design. We also show how to carry out sound statistical inference based on such an adaptive sampling scheme (therefore extending some results known in the independent and identically distributed setting only so far), and how group‐sequential testing applies on top of it. The procedure is robust (i.e. consistent even if the working model is mis‐specified). A simulation study confirms the theoretical results and validates the conjecture that the procedure may also be efficient.     

Smooth estimation of a monotone density

We investigate the interplay of smoothness and monotonicity assumptions when estimating a density from a sample of observations. The nonparametric maximum likelihood estimator of a decreasing density on the positive half line attains a rate of convergence of [Formula: See Text] at a fixed point t if the density has a negative derivative at t. The same rate is obtained by a kernel estimator of bandwidth [Formula: See Text], but the limit distributions are different. If the density is both differentiable at t and known to be monotone, then a third estimator is obtained by isotonization of a kernel estimator. We show that this again attains the rate of convergence [Formula: See Text], and compare the limit distributions of the three types of estimators. It is shown that both isotonization and smoothing lead to a more concentrated limit distribution and we study the dependence on the proportionality constant in the bandwidth. We also show that isotonization does not change the limit behaviour of a kernel estimator with a bandwidth larger than [Formula: See Text], in the case that the density is known to have more than one derivative.     

Skill and education effects on earnings in 18 Countries: The role of national educational institutions

This study investigates whether the mechanisms why education is rewarded vary across countries. Do educational institutions affect the likelihood that support for a particular mechanism is found? Combining IALS survey data and OECD statistics on educational institutions, it was shown that the effect of measured skill on earnings - controlled for educational attainment - is lower in countries where educational institutions produce skills relevant for work through the vocational system. This indicates that the human capital perspective on education works particularly well in vocationally oriented educational systems, as the skills generated in education are strongly overlapping with the skills that are rewarded. An alternative mechanism sees education as a means for social closure through credentialization. Under the credentialization model, education is not primarily rewarded for the productivity-enhancing skills it entails, but rather for reasons unrelated to productivity. Following this theory education is used for selection into the organization, after which directly observable skills are determining wages. Assuming that a strongly differentiated educational system creates boundaries between social groups, it is hypothesized that strongly differentiated systems lead to stronger measured skill effects. We do not find support for this hypothesis.     

Weiterbilden und Weiterkommen? Non-formale berufliche Weiterbildung und Arbeitsmarktmobilität in Deutschland

Politicians and the business leaders regularly stress the importance of (further) education for individual life chances. Still, it is far from clear whether non-formal further training, i.?e. short training courses, which are the most common forms of further education in Germany, lead to career advancement. In this study, we analyze the impact of non-formal further training on labor market mobility using data from the German National Educational Panel Study (NEPS) over the period from 2009 to 2016. Event history models for discrete time intervals show that employer-provided courses reduce mobility and promote career stability, which contradicts hypotheses derived from human capital theory, which is commonly used in the literature. More concretely, employer-provided courses prevent downward mobility (safety net function), but also reduce upward mobility and firm changes. Based on these findings, we suggest that future research should consider transaction costs and the firm context as well as the distinction between employer-provided and non-employer-provided training.