Psychological correlates of fatigue: Examining depression, perfectionism, and automatic negative thoughts

This study investigated whether depression, perfectionism or automatic negative thoughts would correlate with the symptomatology of fatigue in a non-clinical population. A structural model was developed to determine if depression or latent constructs of perfectionism and automatic negative thoughts would correlate with four components of fatigue (emotional distress, somatic symptomatology, general fatigue and cognitive difficulties). It was found that all aspects of fatigue were significantly correlated with depression and automatic negative thoughts, whereas only emotional distress and cognitive difficulties were correlated with perfectionism.Social Sciences and Humanities Research Counci

The effects of heteroscedasticity on tests of equivalence

Tests of equivalence, which are designed to assess the similarity of group means, are becoming more popular, yet very little is known about the statistical properties of these tests. Monte Carlo methods are used to compare the test of equivalence proposed by Schuirmann with modified tests of equivalence that incorporate a heteroscedastic error term. It was found that the latter were more accurate than the Schuirmann test in detecting equivalence when sample sizes and variances were unequal.Social Sciences and Humanities Research Counci

Recommendations for applying tests of equivalence

Researchers in psychology reliably select traditional null hypothesis significance tests (e.g., Student's t test), regardless of whether the research hypothesis relates to whether the group means are equivalent or whether the group means are different. Tests of equivalence, which have been popular in biopharmaceutical studies for years, have recently been introduced and recommended to researchers in psychology for demonstrating the equivalence of two group means. However, very few recommendations exist for applying tests of equivalence. A Monte Carlo study was used to compare the test of equivalence proposed by Schuirmann with the traditional Student t test for deciding if two group means are equivalent. It was found that Schuirmann's test of equivalence is more effective than Student's t test at detecting population mean equivalence with large sample sizes; however, Schuirmann's test of equivalence performs poorly relative to Student's t test with small sample sizes and/or inflated variances.Social Sciences and Humanities Research Counci

Evaluating the equivalence of, or difference between, psychological treatments: An exploration of recent intervention studies

In behavioral science research there is often the need to determine if an outcome variable differs, or is equivalent, across groups. Significance tests are the most prevalently applied data analysis method for this type of question. The purpose of this study was to examine how statistical tests for equivalence and difference have been applied to compare clinical interventions. Peer-reviewed journal articles that made treatment comparisons were examined. For each study, the primary hypothesis, statistical test usage, and the stated conclusion were recorded. Of the 270 studies investigated, 54.4% inappropriately made equivalence-based conclusions from difference-based test statistics (e.g., t test, ANOVA). Significance tests are often applied as a matter of course regardless of the research question. We have found that difference tests are similarly favored and have been applied to examine difference and inappropriately applied to examine equivalence. We discuss our findings and provide resources for researchers who want to statistically evaluate between-groups equivalence.Social Sciences and Humanities Research Council (SSHRC

Evaluating clinical significance through equivalence testing: Extending the normative comparisons approach

The field of psychology, as with many other disciplines, has been increasingly interested in being able to measure the effectiveness of behavioral interventions. This trend has led to a number of different approaches for measuring clinical significance, each addressing a slightly different aspect of the clinical outcome. Recently, clinical psychologists (and clients) have supported the contention that one of the most important therapeutic questions is whether clients are functioning equivalently to normal controls following an intervention. To address this question, Kendall, Marrs-Garcia, Nath, and Sheldrick (1999) presented an approach to measuring clinical significance that utilizes tests of equivalence. The present study clarifies the nature of the hypotheses being conducted in measuring clinical significance with tests of equivalence and extends the approach by incorporating recent advances in equivalence testing. A revised approach for evaluating clinical significance via equivalence testing is proposed, and an empirical example demonstrating this approach is provided.Social Sciences and Humanities Research Council (SSHRC

Comparing Means under Heteroscedasticity and Nonnormality: Further Exploring Robust Means Modeling

Comparing the means of independent groups is a concern when the assumptions of normality and variance homogeneity are violated. Robust means modeling (RMM) was proposed as an alternative to ANOVA-type procedures when the assumptions of normality and variance homogeneity are violated. The purpose of this study is to compare the Type I error and power rates of RMM to the trimmed Welch procedure. A Monte Carlo study was used to investigate RMM and the trimmed Welch procedure under several conditions of nonnormality and variance heterogeneity. The results suggest that the trimmed Welch provides a better balance of Type I error control and power than RMM

Psychological Well-Being in Obese Inpatients with Ischemic Heart Disease at Entry and at Discharge from a Four-Week Cardiac Rehabilitation Program

The purposes of this observational pre-post study were twofold: 1- to evaluate psychological health in obese patients with ischemic heart disease at admission to cardiac rehabilitation (CR) and 2 – to examine the effectiveness of a 4-week CR residential program in improving obese patients’ psychological well-being at discharge from CR. A sample of 177 obese patients completed the Psychological General Well-Being Inventory (PGWBI) at admission to the CR program and at discharge. The equivalence testing method with normative comparisons was used to determine the clinical significance of improvements after having established that baseline mean scores on the PGWBI scales were significantly lower than normal means. Results show that patients scored equally or better than norms on many PGWBI dimensions at admission to CR but scored significantly worse on Global Score, Vitality and Self-control. At discharge, mean scores that were impaired at baseline returned to normal levels at the more conservative equivalence interval. A 4-week CR program was thus effective in improving obese patients’ psychological well-being. The equivalence testing method allowed to establish the clinical significance of such improvement

Equivalence based tests of clinical significance: Assessing treatments for depression

Treatment efficacy is largely determined by statistical significance testing, and clinical significance testing is often used to quantify or qualify the efficacy of a treatment at the individual or group level. This study applies the equivalence based clinical significance model proposed by Kendall, Marrs-Garcia, Nath and Sheldrick (1999), and a revised model proposed by Cribbie and Arpin-Cribbie (2009), to the assessment of treatments for depression. Using several studies that investigated treatments for depression, we tested whether the post-treatment means were equivalent to the means for a similar normal comparison group. All of the studies had significant improvement from pretest to posttest, although for many of the studies the treated group was not equivalent to a normal comparison group at posttest. Further, there are important differences between the conclusions drawn from the Kendall et al. and Cribbie and Arpin-Cribbie methods for assessing equivalence based clinical significance.Social Sciences and Humanities Research Council (SSHRC

Equivalence of Population Variances: Synchronizing the Objective and Analysis

Researchers are often interested in testing for the equivalence of population variances. Traditional difference-based procedures are appropriate to answer questions about differences in some statistic (e.g., variances, etc.). However, if a researcher is interested in evaluating the equivalence of population variances, it is more appropriate to use a procedure specifically designed to determine equivalence. A simulation study was used to compare newly developed equivalence-based tests to difference-based variance homogeneity tests under common data conditions. Results demonstrated that traditional difference-based tests assess equality of variances from the wrong perspective, and that the proposed Levene-Wellek-Welch test for equivalence of group variances using the absolute deviations from the median was the best performing test for detecting equivalence. An R function is provided in order to facilitate use of this test for equivalence of population variances.SSHR

Exploring the utility of the Multidimensional State Boredom Scale.

Background: State boredom–the experience of boredom in the moment – is related to a number of psychosocial issues. Until the recent creation of the Multidimensional State Boredom Scale (MSBS), research was constrained by the lack of a comprehensive, validated measure. However, the MSBS could benefit from further evaluation. Aim: To more thoroughly validate the MSBS. Methods: In two studies, participants were induced into a state of either boredom or non-boredom, and then completed the MSBS. Results: Discriminant analysis showed that the full MSBS was able to correctly classify 68.1% (Study 2) – 84.1% (Study 1) of participants into their experimental condition. Based on 14 further DA analysis, a subset of eight items (a potential short form) is proposed. Differential item functioning (Study 1) found only one item to which responding differed by gender. Discussion: Use of the MSBS, including the full scale versus the short form, is discussed. Which experiential components of boredom may be particularly important for classifying bored individuals, and the issue of variability across boredom manipulations, are also considered