Repeated measures one‐way ANOVA based on a modified one‐step M‐estimator

Wilcox, Keselman, Muska and Cribbie (2000) found a method for comparing the trimmed means of dependent groups that performed well in simulations, in terms of Type I errors, with a sample size as small as 21. Theory and simulations indicate that little power is lost under normality when using trimmed means rather than untrimmed means, and trimmed means can result in substantially higher power when sampling from a heavy‐tailed distribution. However, trimmed means suffer from two practical concerns described in this paper. Replacing trimmed means with a robust M‐estimator addresses these concerns, but control over the probability of a Type I error can be unsatisfactory when the sample size is small. Methods based on a simple modification of a one‐step M‐estimator that address the problems with trimmed means are examined. Several omnibus tests are compared, one of which performed well in simulations, even with a sample size of 11.     

Comparing groups in a before–after design: When t test and ANCOVA produce different results

Background. Researchers often test people before and after some treatment and compare these scores with a control group. Sometimes it is not possible to allocate people into conditions randomly, which means the initial scores for the two groups may differ. There are two main approaches: t test on the gain scores and ANCOVA partialling out the initial scores. Lord (1967) showed that these can lead to different conclusions. This is an often‐discussed paradox in psychology and education. Aims. The reasons why these approaches can lead to different conclusions, the assumptions that each approach makes and how the approaches relate to group allocation, are discussed Methods. Three sets of simulations are reported that investigate the relationships among effect size, group allocation, measurement error and Lord's paradox. Conclusions. Recommendations are given that stress careful examination of the research questions, sampling and allocation of participants and graphing the data. ANCOVA is appropriate when allocation is based on the initial scores, t test can be appropriate if allocation is associated non‐causally with the initial scores, but often neither approach provides adequate results.     

Reaction time and intelligence: Comparing associations based on two response modes

People who score highly on intelligence tests also tend to have faster and less variable reaction times. Effect size estimates for the reaction time–intelligence association are larger in samples that are more representative of the population. However, such samples have often been tested on a reaction time device that requires reading a number and processing its association with a specific response location (Cox, Huppert, & Whichelow, 1993). Here, we use this device and another reaction time device (Dykiert et al., 2010) that is similar, except that the responses require less processing; subjects simply press a button that is adjacent to the stimulus light. We focus on the possibility that lights as stimuli require less higher-order cognitive engagement than numbers, and then test whether parameters from these two tasks are highly correlated and similarly associated with age and higher cognitive abilities. Both tasks measured simple and choice reaction times and their intra-individual variation across trials. The parameters of the two tasks were very highly correlated and parameters from both tasks were similarly associated with age, social factors, and differences in higher cognitive abilities. The respective choice reaction time parameters from either task accounted for much of the age- and higher cognitive ability-associations of the other task's parameters. These findings are important in establishing that the effect sizes of higher cognitive ability associations with processing speed measures may be found when the processing demands are minimal.     

A meta‐mood model of rumination and depression: Preliminary test in a non‐clinical population

Depressive rumination and trait meta‐mood (emotional attention, emotional clarity and emotional repair) have been suggested as vulnerability factors leading to depression, but less is known about the associations among them. In this study, we examined the relationships between trait meta‐mood, rumination and depressive symptomatology. Using structural equation analysis in a large sample of a non‐clinical population we found a preliminary test of the role of trait meta‐mood dimensions in rumination and depressive symptomatology. Results indicated that attention to feelings has two pathways in its relation with rumination and depressive mood. On the one hand, emotional attention was associated with emotional clarity, and emotional clarity with emotional repair, which was related to lower depressive symptomatology, in part, by reducing rumination. On the other hand, emotional attention was directly associated with ruminative thoughts which, in turn, were related to higher depressive mood. Findings are discussed in terms of the implications of beliefs about emotions in the treatment of depression.     

Surface‐ and deep‐level dissimilarity effects on social integration and individual effectiveness related outcomes in work groups: A meta‐analytic integration

Prior research linking demographic (e.g., age, ethnicity/race, gender, and tenure) and underlying psychological (e.g., personality, attitudes, and values) dissimilarity variables to individual group member's work‐related outcomes produced mixed and contradictory results. To account for these findings, this study develops a contingency framework and tests it using meta‐analytic and structural equation modelling techniques. In line with this framework, results showed different effects of surface‐level (i.e., demographic) dissimilarity and deep‐level (i.e., underlying psychological) dissimilarity on social integration, and ultimately on individual effectiveness related outcomes (i.e., turnover, task, and contextual performance). Specifically, surface‐level dissimilarity had a negative effect on social integration under low but not under high team interdependence. In return, social integration fully mediated the negative relationship between surface‐level dissimilarity and individual effectiveness related outcomes under low interdependence. In contrast, deep‐level dissimilarity had a negative effect on social integration, which was stronger under high and weaker under low team interdependence. Contrary to our predictions, social integration did not mediate the negative relationship between deep‐level dissimilarity and individual effectiveness related outcomes but suppressed positive direct effects of deep‐level dissimilarity on individual effectiveness related outcomes. Possible explanations for these counterintuitive findings are discussed.     

Work‐group and organizational support: A test of distinct dimensions

Using data from 467 members of a large firm in the United States, this paper found that perceived work‐group support is a distinct construct from perceived organizational support. To reinforce the uniqueness of the constructs, the work‐group and organizational support constructs exhibited meaningful, differential relationships with six of eight variables reflecting different levels of exchange relationships and commitments. The implications of these findings are discussed.     

The effects of pay level on organization‐based self‐esteem and performance: A field study

Most compensation managers implicitly assume (or perhaps hope) that high pay levels will maintain and enhance future performance. To date, this assumption has been largely untested. Given the importance of pay level and the large expense that pay represents to most organizations, understanding how and why pay level influences the behaviour of employees in organizations is an important question. The purpose of this study is to examine the motivational effects of pay level on employee performance. To examine these issues, we collected field study data from a variety of sources, at three different times, and assessed the effects of employee pay level on subsequent self‐esteem and performance. Specifically, we hypothesized that the effects of pay level on performance would be mediated by pay level effects on organization‐based self‐esteem. We base this hypothesis on the premise that level of pay within an organization communicates a sense of how much the organization values an employee and thus affects employee organization‐based self‐esteem which, in turn, enhances job performance. After controlling for organization tenure, and previous pay change, results supported a mediated model that suggests that pay level affects employee self‐esteem, which in turn, affects employee performance.     

A test of foreign language acquisition: paired‐association learning

This experiment investigated college student difficulties with foreign language acquisition. We developed a word‐sound, paired‐associates learning test that discriminated 92% of the control participants and 95% of the experimental participants. The results are interpreted in terms of an associative model of foreign language learning disability. We discuss how to integrate the test into a larger diagnostic battery for predicting the facility with which a person will be able to learn a foreign language. Copyright © 2002 John Wiley & Sons, Ltd.     

Trauma‐focused CBT with maltreated children: A clinic‐based evaluation of a new treatment manual

The effectiveness of a locally developed trauma‐focused cognitive behavioural therapy (TF‐CBT) program for maltreated children with post‐traumatic stress disorder (PTSD) was examined across different therapists in a child protection clinic setting. An earlier phase of the research piloting the program had provided promising results. This second phase involved two studies evaluating the completed TF‐CBT manual delivered by (a) the developer and (b) other therapists. A single‐case multiple‐baseline design was used to demonstrate the controlling effects of the treatment on PTSD symptoms and child coping. Eight 9–13‐year‐old abused children with PTSD were treated. Positive outcomes support the effectiveness of the TF‐CBT program delivered by both the developer and other therapists. The study design and methodology were robust enough to confirm empirically the clinically beneficial effects and potential for this new program. It was also apparent, however, from study limitations, including missing data for some patients, that there are a number of challenges in carrying out such research in a busy child protection service setting with multiply‐abused patients. This paper considers implications and ways forward for engaging in empirically supported practice as well as future development and research.     

How the 2SLS/IV estimator can handle equality constraints in structural equation models: A system‐of‐equations approach

Parameters in structural equation models are typically estimated using the maximum likelihood (ML) approach. Bollen (1996) proposed an alternative non‐iterative, equation‐by‐equation estimator that uses instrumental variables. Although this two‐stage least squares/instrumental variables (2SLS/IV) estimator has good statistical properties, one problem with its application is that parameter equality constraints cannot be imposed. This paper presents a mathematical solution to this problem that is based on an extension of the 2SLS/IV approach to a system of equations. We present an example in which our approach was used to examine strong longitudinal measurement invariance. We also investigated the new approach in a simulation study that compared it with ML in the examination of the equality of two latent regression coefficients and strong measurement invariance. Overall, the results show that the suggested approach is a useful extension of the original 2SLS/IV estimator and allows for the effective handling of equality constraints in structural equation models.     

Changes in personality in pre‐ and post‐dialectical behaviour therapy borderline personality disorder groups: A question of self‐control

Dialectical behaviour therapy (DBT) is an evidence‐based therapy for people with borderline personality disorder (BPD). Past research has identified behavioural changes indicating improved functioning for people who undergo DBT. To date, however, there has been little research investigating the underlying mechanism of change. The present study utilised a between‐subjects design and self‐report questionnaires of Self‐Control and the five factor model of personality and drew participants from a metropolitan DBT program. We found that pre‐treatment participants were significantly lower on Self‐Control, Agreeableness and Conscientiousness when compared to both the post‐treatment assessment and the norms for each questionnaire. Neuroticism was significantly higher both before and after treatment when compared to the norms. These findings suggest that Self‐Control may play a role in both the presentation of this disorder and the effect of DBT. High levels of Neuroticism lend weight to the Linehan biosocial model of BPD development.     

An alternative to Cohen's standardized mean difference effect size: a robust parameter and confidence interval in the two independent groups case

The authors argue that a robust version of Cohen's effect size constructed by replacing population means with 20% trimmed means and the population standard deviation with the square root of a 20% Winsorized variance is a better measure of population separation than is Cohen's effect size. The authors investigated coverage probability for confidence intervals for the new effect size measure. The confidence intervals were constructed by using the noncentral t distribution and the percentile bootstrap. Over the range of distributions and effect sizes investigated in the study, coverage probability was better for the percentile bootstrap confidence interval.     

A meta‐analysis of the predictors and consequences of organization‐based self‐esteem

Organization‐based self‐esteem (OBSE), which represents employees' beliefs about their own value and competence as organizational members, has attracted much recent research attention. In the current paper, we identified several theoretically based predictors and consequences of OBSE. We then conducted a meta‐analysis examining the relationships between OBSE and these variables. Results indicated that several hypothesized predictors, including the work environment and employee dispositions, were related to OBSE. Furthermore, OBSE was related to several hypothesized outcome variables including job satisfaction, organizational commitment, employee health, job performance, and organizational citizenship behaviour. As expected, OBSE generally yielded stronger relationships with work‐related variables than did general self‐esteem and we found evidence that OBSE mediated the relationships between general self‐esteem and work‐related criteria.     

Expectancy‐effects without expectancies: Illusory correlations based on cue‐overlap

Expectancy‐based illusory correlations have been observed in numerous experiments. Simulations using the connectionist computer model BIAS (Fiedler, 1996 ) show that such illusory correlations may not always reflect expectancy biases but influences of similarity via cue‐overlap. Cue‐overlap means that some of the probabilistic cues that indicate the presence of one variable are also indicative of another variable. In an experiment, participants learned two novel concepts pertaining to a fictitious painter and a fictitious artistic style in separate runs. Both concepts were defined by multiple probabilistic cues observable in paintings. For half the participants, the cue systems underlying the perception of the two concepts overlapped, whereas for the other half they did not. In addition, we manipulated whether or not participants expected a positive contingency between artist and artistic style. In the second part of the experiment, a series of paintings was presented that constituted an objective zero correlation between artist and artistic style. Participants' subsequent contingency judgments were assessed by direct and indirect measures. Data analyses revealed main effects for expectancy induction and cue‐overlap but no interaction on the direct measure and nearly identical results on the indirect measure. Thus, cue‐overlap and expectancy induction independently triggered the development of illusory correlations. Copyright © 2000 John Wiley & Sons, Ltd.     

Gender and reward distributions: A test of two hypotheses

This study was designed as a test of two competing explanations of gender differences in distributive justice: (a) the equity-equality hypothesis, which states that males endorse equitable distributions more than females and females endorse equal distributions more than males; and (b) the exploitation-accommodation hypothesis, which states that the sexes vary their norm endorsement according to self-favoring (males) or other-favoring (females) distribution outcomes. Preadolescent and college-aged subjects rated the fairness of reward distributions of vignette characters who had contributed either more or less than a co-worker in a task, and had subsequently divided the rewards either equitably or equally. The data provided no support for the equity-equality hypothesis, but did support the exploitation-accommodation hypothesis. Specifically, females rated equitable distributions of inferior workers as more fair than males did. Thus, the popular conclusion that males have a stronger commitment to equity than females must be rejected.