A note on robustness of D-optimal block designs for two-colour microarray experiments

Two-colour microarray experiments form an important tool in gene expression analysis. Due to the high risk of missing observations in microarray experiments, it is fundamental to concentrate not only on optimal designs but also on designs which are robust against missing observations. As an extension of Latif et al. (2009), we define the optimal breakdown number for a collection of designs to describe the robustness, and we calculate the breakdown number for various D-optimal block designs. We show that, for certain values of the numbers of treatments and arrays, the designs which are D-optimal have the highest breakdown number. Our calculations use methods from graph theory.     

Marriage Migration Versus Family Reunification: How Does the Marriage and Migration History Affect the Timing of First and Second Childbirth Among Turkish Immigrants in Germany?

Our study focuses on the fertility of first-generation female and male Turkish migrants in Germany. To evaluate whether timing effects such as fertility disruption or an interrelation of marriage, migration and childbirth occur, we examine first and second births in the years before and after immigration to Germany. The Turkish sample of the Generations and Gender Survey which was conducted in 2006 offers the unique opportunity to examine Turkish immigrants as a single immigrant category. We question the common understanding that Turkish immigrants who arrived to Germany after 1973 mainly arrived for family reunification resulting in high birth intensities immediately after immigration. To distinguish different circumstances under which male and female immigrants have arrived to Germany, we include the combined marriage and migration history of the couple. We find that first birth probabilities are elevated during the years immediately following migration. But this effect is not universal among migrants with different marriage and migration histories. It appears that the arrival effect of high birth intensities is particularly high among female immigrants and is evident only among marriage migrants, that is Turks who married a partner who already lived in Germany at the time of the wedding. By contrast, among those who immigrated for family reunification, we do not find such an arrival effect.     

Insurance demand and social comparison: An experimental analysis

This paper analyzes whether social comparison can explain the low take-up of disaster insurance usually reported in field studies. We argue that risks in the case of disasters are highly correlated between subjects whereas risks for which high insurance take-up can be observed (e.g. extended warranties or cell phone insurance) are typically idiosyncratic. We set up a simple model with social reference points and show that in the presence of inequality aversion social comparison makes insurance indeed less attractive if risks are correlated. In addition we conducted a simple experiment which confirms these theoretical results. The average willingness to pay for insurance is significantly higher for idiosyncratic than for correlated risks.     

Further specification of the leader political skill–leadership effectiveness relationships: Transformational and transactional leader behavior as mediators

The present investigation was a three-source test of the intermediate linkages in the leader political skill–leader effectiveness and follower satisfaction relationships, which examined transformational and transactional (i.e., contingent reward behavior) leader behavior as mediators. Data from 408 leaders (headmasters) and 1429 followers (teachers) of state schools in the western part of Germany participated in this research. The results of mediation analyses, based on bias-corrected bootstrapping confidence intervals, provided support for the hypotheses that political skill predicts both transformational and transactional leader behavior, beyond other established predictors, and that transformational and transactional leader behavior mediate the relationships between leader political skill and leadership effectiveness. The contributions to theory and research, strengths and limitations, directions for future research, and practical implications are discussed.     

Teacher shortages, teacher contracts and their effect on education in Africa

Summary.  To enhance primary enrolment rates, many African countries have launched large teacher recruitment programmes in recent years. Given tight budgetary constraints, teachers are no longer employed in civil service positions, but on the basis of (fixed term) contracts typically implying considerably lower salaries and a sharply reduced amount of professional training. We analyse the effect of this change on educational quality in Niger, Togo and Mali, on the basis of very informative data, which are comparable across these countries. We use a variety of estimation techniques, including a non-parametric estimation of quantile treatment effects. Our results demonstrate that contract teachers tend to reduce inequalities in student outcomes. Overall, the effects are positive in Mali, somewhat mixed in Togo and negative in Niger. This ordering is consistent with theoretical expectations related to the manner in which contract teacher programmes were implemented differently in each of the three countries under study.     

Freiwillige in Organisationen — störend oder bereichernd? Merkmale einer gelingenden Integration

Volunteers in organizations — problem or asset? Characteristics of successful integrationVolunteering in Germany is on the rise. The expectations of the volunteers regarding their work are shifting from altruistic to self centered motives. Organizations have to respond to these changes and implement a specific management of volunteers. Also in counseling of organizations and their members, specific measures have to be developed to sharpen their view on potential conflict.     

I. Soziologie und Politik in guter Gesellschaft?

Ohne Zusammenfassung