Meta-Analysis of Raw Mean Differences.

This article discusses the meta-analysis of raw mean differences. It presents a rationale for cumulating psychological effects in a raw metric and compares raw mean differences to standardized mean differences. Some limitations of standardization are noted, and statistical techniques for raw meta-analysis are described. These include a graphical device for decomposing effect sizes. Several illustrative data sets are analyzed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of directionality of significance tests on the bias of accessible effect sizes.

The proportion of studies that use one-tailed statistical significance tests (π) in a population of studies targeted by a meta-analysis can affect the bias of the sample effect sizes (sample ESs, or ds) that are accessible to the meta-analyst. H. C. Kraemer, C. Gardner, J. O. Brooks, and J. A. Yesavage (1998) found that, assuming π?=?1.0, for small studies (small Ns) the overestimation bias was large for small population ESs (δ?=?0.2) and reached a maximum for the smallest population ES (viz., δ?=?0). The present article shows (with a minor modification of H. C. Kraemer et al.'s model) that when π?=?0, the small-N bias of accessible sample ESs is relatively small for δ?≤?0.2, and a minimum (in fact, nonexistent) for δ?=?0. Implications are discussed for interpretations of meta-analyses of (a) therapy efficacy and therapy effectiveness studies, (b) comparative outcome studies, and (c) studies targeting small but important population ESs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the Use of Beta Coefficients in Meta-Analysis.

This research reports an investigation of the use of standardized regression (beta) coefficients in meta-analyses that use correlation coefficients as the effect-size metric. The investigation consisted of analyzing more than 1,700 corresponding beta coefficients and correlation coefficients harvested from published studies. Results indicate that, under certain conditions, using knowledge of corresponding beta coefficients to impute missing correlations (effect sizes) generally produces relatively accurate and precise population effect-size estimates. Potential benefits from applying this knowledge include smaller sampling errors because of increased numbers of effect sizes and smaller nonsampling errors because of the inclusion of a broader array of research designs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

requivalent: A Simple Effect Size Indicator.

The purpose of this article is to propose a simple effect size estimate (obtained from the sample size, N, and a p value) that can be used (a) in meta-analytic research where only sample sizes and p values have been reported by the original investigator, (b) where no generally accepted effect size estimate exists, or (c) where directly computed effect size estimates are likely to be misleading. This effect size estimate is called requivalent because it equals the sample point-biserial correlation between the treatment indicator and an exactly normally distributed outcome in a two-treatment experiment with N/2 units in each group and the obtained p value. As part of placing requlvaient into a broader context, the authors also address limitations of requivalent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organizational Partnerships in China: Self-Interest, Goal Interdependence, and Opportunism.

Opportunism in organizational partnerships may be understood in terms of how partners conclude that their self-interests are related to each other. When partners believe that their goals are competitively but not cooperatively related, they are tempted to pursue their self-interests opportunistically. Cognitive understandings and values of a shared vision may help partners believe their goals are cooperatively related. Results from 103 pairs of customer and supplier organizations support the argument that partnerships are not inevitably threatened by opportunism. Using structural equation analysis, the authors suggested that shared vision can help partners develop cooperative goals that lead to low levels of opportunism. These results suggest that a shared vision and cooperative goals are important foundations for effective organizational partnerships. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A Note on Testing for Homogeneity Among Effect Sizes Sharing a Common Control Group.

L. V. Hedges and I. Olkin (1985) presented a statistic to test for homogeneity among correlated effect sizes and L. J. Gleser and I. Olkin (1994) presented a large-sample approximation to the covariance matrix of the correlated effect sizes. This article presents a more exact expression for this covariance matrix, assuming normally distributed data but not large samples, for the situation where effect sizes are correlated because a single control group was compared with more than one treatment group. After the correlation between effect sizes has been estimated, the standard Q statistic for correlated effect sizes can be used to test for homogeneity. This method is illustrated using results from schizophrenia research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Comment on Sampling Error in the Standardized Mean Difference With Unequal Sample Sizes: Avoiding Potential Errors in Meta-Analytic and Primary Research.

The authors discuss potential confusion in conducting primary studies and meta-analyses on the basis of differences between groups. First, the authors show that a formula for the sampling error of the standardized mean difference (d) that is based on equal group sample sizes can produce substantially biased results if applied with markedly unequal group sizes. Second, the authors show that the same concerns are present when primary analyses or meta-analyses are conducted with point-biserial correlations, as the point-biserial correlation (r) is a transformation of d. Third, the authors examine the practice of correcting a point-biserial r for unequal sample sizes and note that such correction would also increase the sampling error of the corrected r. Correcting rs for unequal sample sizes, but using the standard formula for sampling error in uncorrected r, can result in bias. The authors offer a set of recommendations for conducting meta-analyses of group differences. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Team Goal Commitment and Team Effectiveness: The Role of Task Interdependence and Supportive Behaviors.

The objectives of this study were to test the relationships between team goal commitment and 3 criteria of team effectiveness (i.e., team performance, quality of group experience, and team viability) as well as to examine the moderating effect of task interdependence and the mediating role of supportive behaviors. Data were gathered from a sample of 74 teams working in 13 Canadian organizations. Results indicated that team goal commitment is positively related to all 3 criteria of team effectiveness. In addition, task interdependence moderates the relationship between team goal commitment and team performance. Furthermore, supportive behaviors mediate the relationships that team goal commitment has with team performance and the quality of group experience. Implications of these findings and future research needs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Meta-analysis of correlation coefficients: A Monte Carlo comparison of fixed- and random-effects methods.

The efficacy of the Hedges and colleagues, Rosenthal-Rubin, and Hunter-Schmidt methods for combining correlation coefficients was tested for cases in which population effect sizes were both fixed and variable. After a brief tutorial on these meta-analytic methods, the author presents 2 Monte Carlo simulations that compare these methods for cases in which the number of studies in the meta-analysis and the average sample size of studies were varied. In the fixed case the methods produced comparable estimates of the average effect size; however, the Hunter-Schmidt method failed to control the Type I error rate for the associated significance tests. In the variable case, for both the Hedges and colleagues and Hunter-Schmidt methods, Type I error rates were not controlled for meta-analyses including 15 or fewer studies and the probability of detecting small effects was less than .3. Some practical recommendations are made about the use of meta-analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interdependence in women with breast cancer and their partners: An interindividual model of distress.

Objective: The aim of this investigation was to test whether interdependence in dyads living with breast cancer could account for person–partner crossover effects in distress outcomes. Method: The sample consisted of 95 dyads with early-stage breast cancer. By using reciprocal dyadic data from women with breast cancer and their partners, we fit a structural equation model of the actor–partner interdependence model to examine the interaction of participants’ depression and stress in predicting their partner’s health outcomes. Results: Results revealed a pattern of influence whereby the interaction of high levels of depression coupled with high levels of stress in women with breast cancer was associated with lowered physical health and well-being in their partners. Although depression seemed to be the key mechanism in predicting distressing outcomes, when depression was combined with any additional stress, the level of physical distress was significantly greater. Results provided preliminary empirical support for crossover effects in the physical well-being of close relational partners in a cancer-related context. Further, results showed that distressing outcomes need not be limited to emotional distress but can also include physical distress. Conclusions: The findings from this study illustrate why it is not sufficient to concentrate care solely on the patient with cancer. Monitoring the social well-being of patients as they go through the cancer process could be as important as assessing their psychological state or other peripheral biomarkers. This line of inquiry would be advanced by including methods other than self-report in assessments of psychological and physical health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analyzing Nonindependent Outcomes in Couple Therapy Using the Actor-Partner Interdependence Model.

The nonindependent components of couple data require data-analytic strategies tailored to the interpersonal processes occurring between relationship partners. This article examines the benefits of a specifically dyadic analytic method, the actor-partner interdependence model (APIM), for evaluating interpartner influence across time. Both conceptual and methodological features of the APIM are exemplified by applying this model to observations of negative and positive affect and global distress in spouses participating in a randomized trial of couple therapy. In addition to elucidating specific advantages of the APIM relative to alternative data-analytic strategies, the current results shed new light on previous findings from a comparative treatment outcome study evaluating behavioral and insight-oriented approaches to couple therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Meta-Analysis of Intellectual and Neuropsychological Test Performance in Attention-Deficit/Hyperactivity Disorder.

Cognitive measures are used frequently in the assessment and diagnosis of attention-deficit/hyperactivity disorder (ADHD). In this meta-analytic review, the authors sought to examine the magnitude of differences between ADHD and healthy participants on several commonly used intellectual and neuropsychological measures. Effect sizes for overall intellectual ability (Full Scale IQ; FSIQ) were significantly different between ADHD and healthy participants (weighted d = .61). Effect sizes for FSIQ were significantly smaller than those for spelling and arithmetic achievement tests and marginally significantly smaller than those for continuous performance tests but were comparable to effect sizes for all other measures. These findings indicate that overall cognitive ability is significantly lower among persons with ADHD and that FSIQ may show as large a difference between ADHD and control participants as most other measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Introduction to the Special Section on Metric in Meta-Analysis.

A key issue for meta-analysts is how to represent study outcomes--in other words, what is the best metric for study outcomes? This introduction describes four articles in a special section on metric in meta-analysis. Do meta-analyses require standardized measures of study outcome? C. F. Bond, W. L. Wiitala, and F. D. Richard (2003) argue that standardization is often not needed and can obscure results. Another aspect of scaling outcomes is dichotomization. J. Sánchez-Meca, F. Marín-Martínez, and S. Chacón-Moscoso (2003) compare estimators appropriate when a meta-analysis includes treatment-control studies with dichotomized outcomes. Two articles deal with additional design complexities. R. Gillett (2003) describes mean-difference estimators, outlining indices comparable to effects from the t test. S. Olejnik and J. Algina (2003) provide a formula for generalized eta squared and omega squared statistics that are comparable across research designs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A meta-analysis of team-efficacy, potency, and performance: Interdependence and level of analysis as moderators of observed relationships.

Meta-analytic techniques were used to examine level of analysis and interdependence as moderators of observed relationships between task-specific team-efficacy, generalized potency, and performance. Sixty-seven empirical studies yielding 256 effect sizes were identified and meta-analyzed. Results demonstrated that relationships are moderated by level of analysis. Effect sizes were stronger at the team level (ρ=.39) than at the individual level (ρ=.20). At the team level, both team-efficacy and potency had positive relationships with performance (ρs=.41 and .37, respectively). Interdependence significantly moderated the relationship between team-efficacy and performance, but not between potency and performance. The relationship between team-efficacy and performance was stronger when interdependence was high (ρ=.45) than when it was low (ρ=.34). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning Processes in Matching and Oddity: The Oddity Preference Effect and Sample Reinforcement.

Eight pigeons learned either matching (to sample) or oddity (from sample) with or without reward for sample responding. The training stimuli were coarse-white, fine-black, or smooth-mauve gravels in pots with buried grain as the reinforcer. Oddity without sample reward was learned most rapidly, followed by matching with sample reward, oddity with sample reward, and matching without sample reward. Transfer was related to acquisition rate: The oddity group without sample reward showed full (equal to baseline) color and texture transfer; the matching group with sample reward showed partial texture transfer; other groups showed no transfer. Sample reward was shown to determine rate of acquisition of matching and oddity and the oddity preference effect. The results are discussed in terms of item-specific associations operating early in learning prior to any relational learning between sample and comparison stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical Activity and Psychological Well-Being in Advanced Age: A Meta-Analysis of Intervention Studies.

A meta-analysis examined data from 36 studies linking physical activity to well-being in older adults without clinical disorders. The weighted mean-change effect size for treatment groups (dC. = 0.24) was almost 3 times the mean for control groups (dC. = 0.09). Aerobic training was most beneficial (dC. = 0.29), and moderate intensity activity was the most beneficial activity level (dC. = 0.34). Longer exercise duration was less beneficial for several types of well-being, though findings are inconclusive. Physical activity had the strongest effects on self-efficacy (dC.= 0.38), and improvements in cardiovascular status, strength, and functional capacity were linked to well-being improvement overall. Social-cognitive theory is used to explain the effect of physical activity on well-being. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Examining psychokinesis: The interaction of human intention with random number generators--A meta-analysis.

Séance-room and other large-scale psychokinetic phenomena have fascinated humankind for decades. Experimental research has reduced these phenomena to attempts to influence (a) the fall of dice and, later, (b) the output of random number generators (RNGs). The meta-analysis combined 380 studies that assessed whether RNG output correlated with human intention and found a significant but very small overall effect size. The study effect sizes were strongly and inversely related to sample size and were extremely heterogeneous. A Monte Carlo simulation revealed that the small effect size, the relation between sample size and effect size, and the extreme effect size heterogeneity found could in principle be a result of publication bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social Networks, Structural Interdependence, and Marital Quality Over the Transition to Marriage: A Prospective Analysis.

This study examined the relationship between couples' network interdependence and marital quality in a sample of 347 couples that were recruited at the time of their first marriage. Husbands and wives completed separate, self-administered questionnaires at home. Analyses are based on data collected at the time of marriage, at the first anniversary, and at the second anniversary. Results indicated that after marriage, husbands' and wives' friend and family networks became increasingly interdependent. Moreover, the interdependence of the friend and family networks at marriage predicted wives' marital quality at the first anniversary, whereas wives' marital quality at the first anniversary predicted the interdependence of the friend network at the second anniversary. No significant longitudinal relations were observed for husbands. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

标准样品在实验室质量控制中的作用

通过使用标准样品对人员、不同原理的分析方法以及仪器进行质量控制论述,论证了标准样品在实验室质量控制中的作用。     

Assessing heterogeneity in meta-analysis: Q statistic or I2 index?

In meta-analysis, the usual way of assessing whether a set of single studies is homogeneous is by means of the Q test. However, the Q test only informs meta-analysts about the presence versus the absence of heterogeneity, but it does not report on the extent of such heterogeneity. Recently, the I2 index has been proposed to quantify the degree of heterogeneity in a meta-analysis. In this article, the performances of the Q test and the confidence interval around the I2 index are compared by means of a Monte Carlo simulation. The results show the utility of the I2 index as a complement to the Q test, although it has the same problems of power with a small number of studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)