Robustness of parameter and standard error estimates against ignoring a contextual effect of a subject-level covariate in cluster-randomized trials

In experimental research, it is not uncommon to assign clusters to conditions. When analysing the data of such cluster-randomized trials, a multilevel analysis should be applied in order to take into account the dependency of first-level units (i.e., subjects) within a second-level unit (i.e., a cluster). Moreover, the multilevel analysis can handle covariates on both levels. If a first-level covariate is involved, usually the within-cluster effect of this covariate will be estimated, implicitly assuming the contextual effect to be equal. However, this assumption may be violated. The focus of the present simulation study is the effects of ignoring the inequality of the within-cluster and contextual covariate effects on parameter and standard error estimates of the treatment effect, which is the parameter of main interest in experimental research. We found that ignoring the inequality of the within-cluster and contextual effects does not affect the estimation of the treatment effect or its standard errors. However, estimates of the variance components, as well as standard errors of the constant, were found to be biased.     

Negativity and positivity effects in person perception and inference: Ability versus morality

The present paper deals with negativity and positivity effects in trait inferences and impression formation. In the first experiment we tested the suggestion of Skowronski and Carlston (1987) that in the domain of morality negative information is more diagnostic, will therefore receive more weight and result in a negativity effect whereas in the domain of abilities, positive information is more diagnostic resulting in positivity effects. Results of our first experiment support these predictions: negative behavioural information leads to more certain inferences concerning morality and positive behavioural information leads to more certain inferences concerning ability. In a second experiment, we investigated the relative weight of positive versus negative ability-and morality-related traits in an impression formation task. We counterposed traits from both morality and ability domains to see which was the most dominant in determining evaluative impressions. Findings of this second experiment showed strong negativity effects but also revealed that information related to morality is more influential in forming an evaluative impression than equally extreme information related to ability. Theoretical implications of these findings are discussed.     

Attitudinal and Social Factors in Adolescent Smoking: In Search of Peer Group Influence1

The smoking attitudes and behavior of two samples of British 15-year-olds (N = 278) were studied by questionnaire. “Smokers” (anyone who had smoked at all within the previous week) held less negative attitudes about smoking, were more likely to have a father who smoked, and anticipated less parental disapproval of their smoking. When asked to name their five best friends among their classmates, smokers were more likely to name other smokers than were nonsmokers. On the basis of these results, we argue that the notion of “peer group influence” should be reconceptualized in terms of intergroup processes and social identity concerns within the peer group.     

Actors' and Observers' attributions,self-serving bias and positivity bias

An experiment was conducted to investigate the influence of evaluative factors upon preference for situational and dispositional attributions. Subjects listened to a tape recording of a group discussion on smoking, two actors presenting arguments in favour of smoking and two actors arguing against smoking. Subjects were then asked to explain in attributional terms the actors' behaviour and their own smoking behaviour, their evaluation of smoking being separately assessed. Results provided no support for a general self-other attributional difference; subjects did not explain their own behaviour in more situational terms while explaining the behaviour of others in more dispositional terms. Findings indicated that individuals generally attributed positively evaluated behaviour to dispositional factors and negatively evaluated behaviour to situational factors, regardless of attributor role (actor or observer). The results are interpreted as offering support for a positivity bias in attributional preference.     

Judging risk behaviour and risk preference: The role of the evaluative connotation of risk terms

Two experiments investigate the impact of the evaluative connotation of risk terms on the judgment of risk behaviour and on risk preference. In the first experiment we focus on (1) the evaluation congruence of the risk terms with a general risk norm and (2) with subjects' individual risk preference, and its effects on the extremity of judgments of risk behaviour. In the second experiment we address (3) the effects of evaluative connotation of risk terms on risk preference. In the first experiment subjects were presented with four decision problems, each with a risky and a cautious decision option, and were required to judge options. Results showed that the judged discrepancy between the risky and cautious option was larger on scales which were evaluatively congruent with the general risk norm for that specific decision problem or with subjects' individual preference. More specificly, in decision problems for which there was considerable consensus about the risk-norm judgments were more extreme on scales which were congruent with the risk norm, in those problems lacking a clear-cut risk-norm judgments were more extreme on scales congruent with subjects' individual risk preference. In the second experiment we studied the reverse relation between the evaluative connotation of risk terms and risk preference. This experiment demonstrates that using evaluatively biased risk terms can affect risk preference. Using terms which imply a positive evaluation of risk-taking and a negative evaluation of risk avoidance led to increased risk preference, and vice versa. Results are discussed in the context of accentuation theory.     

Illusory correlation and attitude-based vested interest

The present studies test whether having a ‘vested interest’ in a particular outcome affects perceived covariation. Vested interest was defined as a function of whether Dutch university students were in favour or against the implementation of a threatening policy (receiving lectures in English as opposed to the native Dutch). In both studies subjects were told that this policy would be tried out at either their own or another comparable university, and that the university chosen would be the one with the greatest proportion of support for the plan. In Study 1 subjects (n = 151) were presented with statements expressing pro or contra attitudes and arguments to the policy. These were ostensibly derived from students at both universities but university affiliation was not indicated. In Study 2 (n = 114) similar information was provided but the statements were attributed to students from the two universities, such that there was an equal proportion of opposition/support for the plan at both universities. We hypothesized that illusory correlations would reflect the vested interest of attitude such that students opposing the policy would overestimate the proportion of opponents to supporters at their own university compared to those in favour of the policy. The results of both studies supported our hypothesis and they also revealed attitude to be a more important predictor of illusory correlation than perceived personal consequences for themselves. The prediction that illusory correlations would be weaker in Study 2 than in Study 1, because it provides less scope for bias, was not supported. The implications of these findings are discussed.     

Reexamining psychokinesis: comment on Bösch, Steinkamp, and Boller (2006)

H. B?sch, F. Steinkamp, and E. Boller's review of the evidence for psychokinesis confirms many of the authors' earlier findings. The authors agree with B?sch et al. that existing studies provide statistical evidence for psychokinesis, that the evidence is generally of high methodological quality, and that effect sizes are distributed heterogeneously. B?sch et al. postulated the heterogeneity is attributable to selective reporting and thus that psychokinesis is "not proven." However, B?sch et al. assumed that effect size is entirely independent of sample size. For these experiments, this assumption is incorrect; it also guarantees heterogeneity. The authors maintain that selective reporting is an implausible explanation for the observed data and hence that these studies provide evidence for a genuine psychokinetic effect.     

Analysis of genetic influences on the consistency and variability of the Big Five across different stressful situations

Several studies have demonstrated that individual differences in personality traits, known as the Big Five, have a genetic component. These personality traits are considered important predictors of everyday behaviour. In addition to personality traits there are also factors in the environment that govern behaviour. This dual influence on behaviour is statistically reflected in a P × S interaction. This study examines the genetic and environmental influences on the interactions between a person and his daily life environment for the Big Five. Fifty‐seven identical twin pairs and 43 fraternal twin pairs participated in this study. Trait related behaviour was measured in 30 different situations with the aid of an SR inventory. The heritability coefficients for the main effect of P were in the normal range, varying between 0.35 for Agreeableness and 0.53 for Conscientiousness. The heritability coefficients for the P × S interactions were moderately high, explaining between 26% and 69% of the total P × S variance. The consequences of these results for general and behavioural genetic research on the Big Five will be discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Take care! The evaluation of a team-based burnout intervention program for oncology care providers

In this quasi-experimental study among staff of 29 oncology wards, the authors evaluated the effects of a team-based burnout intervention program combining a staff support group with a participatory action research approach. Nine wards were randomly selected to participate in the program. Before the program started (Time 1), directly after the program ended (Time 2), and 6 months later (Time 3), study participants filled out a questionnaire on their work situation and well-being. Results of multilevel analyses showed that staff in the experimental wards experienced significantly less emotional exhaustion at both Time 2 and Time 3 and less depersonalization at Time 2, compared with the control wards. Moreover, changes in burnout levels were significantly related to changes in the perception of job characteristics over time.     

The role of affect in attitudes toward organ donation and donor-relevant decisions

We argue that affect plays a vital role in attitudes toward organ donation and that reluctance to become an organ donor is likely to be related to the experience of affective ambivalence. Assessing the affect associated with organ donation could help to predict donor-relevant decisions. Results of a confirmatory factor analysis on 464 students showed that affective evaluations can be distinguished both from cognitive evaluations and from overall evaluations. As expected, affective evaluations revealed ambivalence (using the ‘Griffin’ measure of ambivalence) toward organ donation, whereas the two other types of evaluations did not. Results of a follow-up study using logistic regression (n?=?85), showed that affective evaluations predicted donor-relevant decisions six months later. The present findings support the proposal to include separate affective evaluations in measures of attitudes to organ donation. More general implications for the measurement and structure of attitudes in health related domains are discussed.