The effect of skewness and kurtosis on the robustness of linear mixed models

This study analyzes the robustness of the linear mixed model (LMM) with the Kenward–Roger (KR) procedure to violations of normality and sphericity when used in split-plot designs with small sample sizes. Specifically, it explores the independent effect of skewness and kurtosis on KR robustness for the values of skewness and kurtosis coefficients that are most frequently found in psychological and educational research data. To this end, a Monte Carlo simulation study was designed, considering a split-plot design with three levels of the between-subjects grouping factor and four levels of the within-subjects factor. Robustness is assessed in terms of the probability of type I error. The results showed that (1) the robustness of the KR procedure does not differ as a function of the violation or satisfaction of the sphericity assumption when small samples are used; (2) the LMM with KR can be a good option for analyzing total sample sizes of 45 or larger when their distributions are normal, slightly or moderately skewed, and with different degrees of kurtosis violation; (3) the effect of skewness on the robustness of the LMM with KR is greater than the corresponding effect of kurtosis for common values; and (4) when data are not normal and the total sample size is 30, the procedure is not robust. Alternative analyses should be performed when the total sample size is 30.     

An evaluation of the MMPI-2 and MMPI-a true response inconsistency (TRIN) scales

The Minnesota Multiphasic Personality Inventory-Adolescent (MMPI-A) and Minnesota Multiphasic Personality Inventory-2 (MMPI-2) True Response Inconsistency (TRIN) scales are measures of acquiescence and non-acquiescence included among the standard validity scales on these instruments. The goals of this study were to evaluate the effectiveness of these scales in detecting varying degrees of acquiescence and non-acquiescence and to evaluate cutoff scores for clinical use. After the removal of invalid protocols from the MMPI-2 and MMPI-A normative samples, each normative sample was randomly divided in half. For each measure, one half of the normative sample served as a comparison group and the other half was modified with increasing degrees (10%, 20%, 30%, 40%, and 50%) of randomly inserted true or false responses. The results for a 9.1% base rate of acquiescence or non-acquiescence provide support for TRIN cutoff scores at or near those presented in the MMPI-A and MMPI-2 manuals.     

Starting research in interaction design with visuals for low-functioning children in the autistic spectrum: a protocol.

On starting to think about interaction design for low-functioning persons in the autistic spectrum (PAS), especially children, one finds a number of questions that are difficult to answer: Can we typify the PAS user? Can we engage the user in interactive communication without generating frustrating or obsessive situations? What sort of visual stimuli can we provide? Will they prefer representational or abstract visual stimuli? Will they understand three-dimensional (3D) graphic representation? What sort of interfaces will they accept? Can we set ambitious goals such as education or therapy? Unfortunately, most of these questions have no answer yet. Hence, we decided to set an apparently simple goal: to design a "fun application," with no intention to reach the level of education or therapy. The goal was to be attained by giving the users a sense of agency--by providing first a sense of control in the interaction dialogue. Our approach to visual stimuli design has been based on the use of geometric, abstract, two-dimensional (2D), real-time computer graphics in a full-body, non-invasive, interactive space. The results obtained within the European-funded project MultiSensory Environment Design for an Interface between Autistic and Typical Expressiveness (MEDIATE) have been extremely encouraging.     

Facial appearance and judgments of credibility: the effects of facial babyishness and age on statement credibility

Researchers have found that facial appearance influences social judgments. For example, evidence has shown that facial babyishness and age affect perceivers' impressions of the stimulus person's veracity. In this experiment, the researchers examined whether these variables also influenced the credibility attributed to written statements purportedly made by these people in addition to several topics of interest in deception-detection research. Undergraduates (N = 270) were presented babyfaced or mature-faced photographs that depicted a child, an adult, or an older individual, in addition to a written truthful or deceptive statement purportedly made by the person in the photograph. Results showed that, as predicted, when the statements were accompanied by babyfaced pictures, participants tended to judge them as truthful, but only if the pictures did not depict children. Also, when the statements were accompanied by childen's pictures, participants tended to judge them as deceptive, but only if the pictures depicted a babyish face. Overall detection accuracy was close to chance and did not correlate with either judgmental confidence or with the respondents' estimated lie-detection accuracy. However, confidence and estimated ability were significantly correlated. Also, more confidence was placed in judgments of truthfulness than in judgments of deceptiveness. Respondents' truth bias and the existence of a veracity effect in the diverse experimental conditions were examined as well.     

Reliability and validity of scores from the Singer-Loomis Type Deployment Inventory

This paper focuses on the Singer-Loomis Type Deployment Inventory (SL-TDI), which is an alternative to the Myers-Briggs Type Indicator (MBTI). The SL-TDI utilizes a continuous, non-forced choice format and therefore is a more accurate representation of Jung's personality theory of psychological types. The purpose of the study reported here is to evaluate the reliability and validity of scores from the SL-TDI. Specifically, the goals were to (a) provide estimates of the internal consistency of SL-TDI scores; (b) evaluate the divergent validity of SL-TDI scores by examination of their relationships with the scores on a social desirability responding measure; and (c) examine the test-retest stability of scores from the SL-TDI. Strong support was found for both the reliability and validity of SL-TDI scores.     

The effects of presentation time on preference for curvature of real objects and meaningless novel patterns

Objects with curved contours are generally preferred to sharp‐angled ones. In this study, we aim to determine whether different presentation times influence this preference. We used images of real objects (experiment 1) and meaningless novel patterns (experiment 2). Participants had to select one of two images from a contour pair, curved and sharp‐angled versions of the same object/pattern. With real objects, the preference for curved versions was greatest when presented for 84 ms, and it faded when participants were given unlimited viewing time. Curved meaningless patterns were preferred when presented for 84 and 150 ms. However, in contrast to real objects, preference for meaningless patterns increased significantly in the unlimited viewing time condition. Participants discriminated poorly between the two versions (curved and sharp‐angled) of the meaningless patterns in the 84‐ and 150‐ms presentations (experiment 3). Therefore, in short times with meaningless patterns, participants selected mostly the curved version without being aware of the difference. In conclusion, presentation time, type of stimulus, and their interaction influence preference for curvature.     

Overdispersion tests in count-data analysis

Count data are commonly assumed to have a Poisson distribution, especially when there is no diagnostic procedure for checking this assumption. However, count data rarely fit the restrictive assumptions of the Poisson distribution. The violation of much of such assumptions commonly results in overdispersion, which invalidates the Poisson distribution. Undetected overdispersion may entail important misleading inferences, so its detection is essential. In this study, different overdispersion diagnostic tests are evaluated through two simulation studies. In Exp. 1, the nominal error rate is compared under different sample sizes and lamda conditions. Analysis shows a remarkable performance of the chi2 df test. In Exp. 2 and 3, statistical power is compared under different sample sizes, lamda, and overdispersion conditions. Chi2 and LR tests provide the highest statistical power.     

Adaptation and validation of the Spanish version of the Sport Anxiety Scale SAS-2 for young athletes

The aim of this study is to design a Spanish version of the Sport Anxiety Scale (SAS-2). The questionnaire, originally developed by the Washington University research group in sport psychology to evaluate anxiety in young athletes, was translated and adapted following the APA protocol and its psychometric properties were assessed through internal consistency analysis, confirmatory factor analysis and validity evidence. The Spanish version of the Sport Anxiety Scale has revealed good internal consistency indexes in each subscale and its factor structure has faithfully replicated the one obtained in the original measure. Results indicate that the adapted version of the questionnaire is an adequate and valid measure for the assessment of anxiety in young athletes.     

Regression-based techniques for statistical decision making in single-case designs

The present study evaluates the performance of four methods for estimating regression coefficients used to make statistical decisions about intervention effectiveness in single-case designs. Ordinary least square estimation is compared to two correction techniques dealing with general trend and a procedure that eliminates autocorrelation whenever it is present. Type I error rates and statistical power are studied for experimental conditions defined by the presence or absence of treatment effect (change in level or in slope), general trend, and serial dependence. The results show that empirical Type I error rates do not approach the nominal ones in the presence of autocorrelation or general trend when ordinary and generalized least squares are applied. The techniques controlling trend show lower false alarm rates, but prove to be insufficiently sensitive to existing treatment effects. Consequently, the use of the statistical significance of the regression coefficients for detecting treatment effects is not recommended for short data series.