Comparison of Methods for Factor Invariance Testing of a 1-Factor Model With Small Samples and Skewed Latent Traits.

A primary underlying assumption for researchers using a psychological scale is that scores are comparable across individuals from different subgroups within the population. In the absence of invariance, the validity of these scores for inferences about individuals may be questionable. Factor invariance testing refers to the methodological approach to assessing whether specific factor model parameters are indeed equivalent across groups. Though much research has investigated the performance of several techniques for assessing invariance, very little work has examined how methods perform under small sample size, and non-normally distributed latent trait conditions. Therefore, the purpose of this simulation study was to compare invariance assessment Type I error and power rates between (a) the normal based maximum likelihood estimator, (b) a skewed-t distribution maximum likelihood estimator, (c) Bayesian estimation, and (d) the generalized structured component analysis model. The study focused on a 1-factor model. Results of the study demonstrated that the maximum likelihood estimator was robust to violations of normality of the latent trait, and that the Bayesian and generalized component models may be useful in particular situations. Implications of these findings for research and practice are discussed.

Reference standards for lean mass measures using GE dual energy x-ray absorptiometry in Caucasian adults.

OBJECTIVE: To develop reference values by age and sex for LM measures using GE-Healthcare DXA systems. METHODS: A de-identified sample was obtained from Ball State University's Clinical Exercise Physiology Laboratory and University of Wisconsin-Milwaukee's Physical Activity & Health Research Laboratory. DXA scans of 2,076 women and 1,251 men were completed using a GE Lunar Prodigy or iDXA. Percentiles (%ile) were calculated for all variables of interest (LM, LMI, %LM, and ALMI) and a factorial ANOVA was used to assess differences for each variable between 10-year age groups and sex, as well as the interaction between age and sex. RESULTS: Men had higher mean total LM, %LM, LMI, and ALMI than women (p<0.01), across all age groups. All LM variables decreased significantly over the 5 decades in men, however in women only total LM, %LM, and ALMI decreased from the youngest to oldest age groups (p<0.01). CONCLUSION: These reference values provide for a more accurate interpretation of GE-Healthcare DXA-derived LM measurements offering clinicians and researchers with an initial resource to aid in the early detection and assessment of LM deficits.

Reference standards for body fat measures using GE dual energy x-ray absorptiometry in Caucasian adults.

BACKGROUND: Dual energy x-ray absorptiometry (DXA) is an established technique for the measurement of body composition. Reference values for these variables, particularly those related to fat mass, are necessary for interpretation and accurate classification of those at risk for obesity-related health complications and in need of lifestyle modifications (diet, physical activity, etc.). Currently, there are no reference values available for GE-Healthcare DXA systems and it is known that whole-body and regional fat mass measures differ by DXA manufacturer. OBJECTIVE: To develop reference values by age and sex for DXA-derived fat mass measurements with GE-Healthcare systems. METHODS: A de-identified sample of 3,327 participants (2,076 women, 1,251 men) was obtained from Ball State University's Clinical Exercise Physiology Laboratory and University of Wisconsin-Milwaukee's Physical Activity & Health Research Laboratory. All scans were completed using a GE Lunar Prodigy or iDXA and data reported included percent body fat (%BF), fat mass index (FMI), and ratios of android-to-gynoid (A/G), trunk/limb, and trunk/leg fat measurements. Percentiles were calculated and a factorial ANOVA was used to determine differences in the mean values for each variable between age and sex. RESULTS: Normative reference values for fat mass variables from DXA measurements obtained from GE-Healthcare DXA systems are presented as percentiles for both women and men in 10-year age groups. Women had higher (p<0.01) mean %BF and FMI than men, whereas men had higher (p<0.01) mean ratios of A/G, trunk/limb, and trunk/leg fat measurements than women. CONCLUSION: These reference values provide clinicians and researchers with a resource for interpretation of DXA-derived fat mass measurements specific to use with GE-Healthcare DXA systems.

Identification of individuals with ADHD using the Dean-Woodcock sensory motor battery and a boosted tree algorithm.

The accurate and early identification of individuals with pervasive conditions such as attention deficit hyperactivity disorder (ADHD) is crucial to ensuring that they receive appropriate and timely assistance and treatment. Heretofore, identification of such individuals has proven somewhat difficult, typically involving clinical decision making based on descriptions and observations of behavior, in conjunction with the administration of cognitive assessments. The present study reports on the use of a sensory motor battery in conjunction with a recursive partitioning computer algorithm, boosted trees, to develop a prediction heuristic for identifying individuals with ADHD. Results of the study demonstrate that this method is able to do so with accuracy rates of over 95 %, much higher than the popular logistic regression model against which it was compared. Implications of these results for practice are provided.

Comparing the effects of various whole-body vibration accelerations on counter-movement jump performance.

While it seems that whole body vibration (WBV) might be an effective modality to enhance physical performance, the proper prescription of WBV for performance enhancement remains unknown. The purpose of this study was to compare the immediate effect of various WBV accelerations on counter movement jump (CMJ) height, the duration of any effect, and differences between men and women. Forty-four participants (33 men, 11 women) participated in no less than four CMJ familiarization sessions and completed all vibration sessions. Participants performed a pre-test (three maximal CMJs), followed randomly by one of five WBV accelerations; 1g (no-WBV control), 2.16g, 2.80g, 4.87g, and 5.83g. Participants performed three maximal CMJs immediately, five, and 10 minutes following each 45 sec WBV session. The mean of the three performances was used and calculated as a percentage of the pre-vibration mean value. A Repeated Measures Analysis of Variance (ANOVA; acceleration x time x gender) model was used to analyze the data. The two-way interactions of acceleration-gender (p = 0.033) and time-gender (p = 0.050) were significant. Women performed significantly better following the 2.80g (p = 0.0064) and 5.83g (p = 0. 0125) WBV sessions compared to the 1g (control) session. Men, however, did not experience performance enhancing effects following any of the vibration sessions. While significant differences did not occur between time in either gender, the effects of the 45 sec WBV session in women were transient, lasting approximately five minutes. During the prescription of WBV, gender should be considered given that the results of this study seem to indicate that men and women respond differently to WBV. The results of this study suggest that WBV might be a useful modality as applied during the pre-competition warm-up. Key pointsWBV accelerations of 2.80g (40 Hz, 2-4 mm) and 5.83g (50 Hz, 4-6 mm) seem to elicit a performance enhancement effect following short-duration (45 sec) exposure in untrained women.The performance enhancement effect of a short-duration is transient, lasting less than 10 minutes following exposure.Men and women might differ in their response to the WBV stimulus, as measured by countermovement jump.

Cortical and subcortical constructs of the dean-woodcock sensory motor battery: a construct validity study.

The factor structure of the Dean-Woodcock Sensory Motor Battery was examined using exploratory factor analysis with promax rotation. Participants (n = 1,651) were composed of 701 neurologically impaired individuals and 950 normal individuals. Three factors, accounting for almost 58.2% of the total test variation, emerged from the data and were labeled Simple Sensory Skills, Motor and Complex Sensory Skills, and Subcortical Motor Skills and Auditory/Visual Acuity. Hypothesized cross loadings were present, especially between the first two factors, which highlighted the parallel nature of sensory-motor skills. The third factor demonstrated the least amount of cross loadings, which reinforced the demarcation of cortical and subcortical motor skills measured by the DWSMB. The results also indicated that the factors were separated by the complexity of the cortical sensory-motor tasks. The factor structure, combined with an analysis of the interfactor correlations, provides evidence for construct validity of the DWSMB.