Application of a two-stage random effects model to longitudinal pulmonary function data from sarcoidosis patients

1989 ◽  
Vol 8 (2) ◽  
pp. 189-200 ◽  
Author(s):  
Pamela M. Vacek ◽  
Ruth M. Mickey ◽  
Dianne Y. Bell
Keyword(s):  
Pulmonary Function ◽  
Random Effects ◽  
Random Effects Model ◽  
Two Stage ◽  
Function Data

Analysis of Data from a Controlled Repeated Measurements Design with Baseline-Dependent Dropouts

Methodology ◽  
2007 ◽  
Vol 3 (2) ◽  
pp. 58-66 ◽  
Author(s):  
John E. Overall ◽  
Scott Tonidandel
Keyword(s):  
Monte Carlo ◽  
Random Effects ◽  
Repeated Measurements ◽  
Random Effects Model ◽  
Two Stage ◽  
Linear Interaction ◽  
Rates Of Change ◽  
Type 1 Error ◽  
Stage Analysis

Abstract. Differences in mean rates of change are of primary interest in many controlled treatment evaluation studies. Generalized linear mixed model (GLMM) procedures are widely conceived to be the preferred method of analysis for repeated measurement designs when there are missing data due to dropouts, but systematic dependence of the dropout probabilities on antecedent or concurrent factors poses a problem for testing the significance of differences in mean rates of change across time in such designs. Controlling for the dependence of dropout probabilities on baseline values poses a special problem because a theoretically correct GLMM random-effects model does not permit including the same baseline score as both covariate and dependent variable. Monte Carlo methods are used herein to evaluate the actual Type 1 error rates and power resulting from two commonly-illustrated GLMM random-effects model formulations for testing the GROUPS × TIMES linear interaction effect in group-randomized repeated measurements designs. The two GLMM model formulations differ by either including or not including baseline scores as a covariate in the attempt to control for imbalance caused by the baseline-dependent dropouts. Results from those analyses are compared with results from a simpler two-stage analysis in which dropout-weighted slope coefficients fitted separately to the available repeated measurements for each subject serve as the dependent variable for an ordinary ANCOVA test for difference in mean rates of change. The Monte Carlo results confirm modestly superior Type 1 error protection but quite superior power for the simpler two-stage analysis of dropout-weighted slope coefficients as compared with those for either of the more mathematically complex GLMM analyses.

scholarly journals Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty

2021 ◽  
Vol 178 (2) ◽  
pp. 313-339
Author(s):  
Michael L. Begnaud ◽  
Dale N. Anderson ◽  
Stephen C. Myers ◽  
Brian Young ◽  
James R. Hipp ◽  
...  
Keyword(s):  
Travel Time ◽  
Random Effects ◽  
Mean Squared Error ◽  
Random Effects Model ◽  
Location Error ◽  
Crust And Upper Mantle ◽  
Time Uncertainty ◽  
Uncertainty Estimates ◽  
Event Location ◽  
Travel Time Uncertainty

AbstractThe regional seismic travel time (RSTT) model and software were developed to improve travel-time prediction accuracy by accounting for three-dimensional crust and upper mantle structure. Travel-time uncertainty estimates are used in the process of associating seismic phases to events and to accurately calculate location uncertainty bounds (i.e. event location error ellipses). We improve on the current distance-dependent uncertainty parameterization for RSTT using a random effects model to estimate slowness (inverse velocity) uncertainty as a mean squared error for each model parameter. The random effects model separates the error between observed slowness and model predicted slowness into bias and random components. The path-specific travel-time uncertainty is calculated by integrating these mean squared errors along a seismic-phase ray path. We demonstrate that event location error ellipses computed for a 90% coverage ellipse metric (used by the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (IDC)), and using the path-specific travel-time uncertainty approach, are more representative (median 82.5% ellipse percentage) of true location error than error ellipses computed using distance-dependent travel-time uncertainties (median 70.1%). We also demonstrate measurable improvement in location uncertainties using the RSTT method compared to the current station correction approach used at the IDC (median 74.3% coverage ellipse).

Skin Color Matters in the Latinx Community: A Call for Action in Research, Training, and Practice

2021 ◽  
pp. 073998632199591
Author(s):  
Milton A. Fuentes ◽  
Jazmin A. Reyes-Portillo ◽  
Petty Tineo ◽  
Kenny Gonzalez ◽  
Mamona Butt
Keyword(s):  
Cultural Diversity ◽  
Random Effects ◽  
Undergraduate Students ◽  
Skin Color ◽  
Clinical Training ◽  
Research Training ◽  
Random Effects Model ◽  
Concerted Effort ◽  
Training And Research

While skin color is relevant and important in the Latinx community, as it is associated with colorism, little is known about how often it is measured or the best way to measure it. This article presents results from two studies examining these key concerns in three prominent journals, where Latinx research is typically published (i.e., the Hispanic Journal of Behavioral Sciences, the Journal of Latinx Psychology, and Cultural Diversity and Ethnic Minority Psychology). Study one examined whether skin color was measured as a variable, and if so, what measures and methodologies were used. A review of articles ( n = 1,137) showed few studies measured skin color in these three journals, with studies that did so relying on various approaches. Study two aimed to assess the reliability of a widely used skin color measure, the Massey-Martin scale, also known as the New Immigrant Survey (NIS) Skin Scale. Using a sample of 169 undergraduate students, self-ratings, coder ratings, and in vivo ratings were obtained and compared. One-way random effects model analyses indicated excellent reliability with minimal variability across the various ratings. Our findings suggest a critical need to engage in a more concerted effort to assess and discuss the relevance and importance of skin color within the Latinx community. The authors offer some suggestions on how to facilitate these efforts in clinical, training, and research arenas.

scholarly journals Gunshot Wounds to the Lumbosacral Spine: Systematic Review and Meta-Analysis

2021 ◽  
pp. 219256822110308
Author(s):  
Andrew Platt ◽  
Mostafa H. El Dafrawy ◽  
Michael J. Lee ◽  
Martin H. Herman ◽  
Edwin Ramos
Keyword(s):  
Systematic Review ◽  
Random Effects ◽  
Surgical Intervention ◽  
Meta Analysis ◽  
Gunshot Wounds ◽  
Operative Management ◽  
Operative Intervention ◽  
Lumbosacral Spine ◽  
Random Effects Model ◽  
Significant Difference

Study Design: Systematic review and meta-analysis. Objectives: Indications for surgical decompression of gunshot wounds to the lumbosacral spine are controversial and based on limited data. Methods: A systematic review of literature was conducted to identify studies that directly compare neurologic outcomes following operative and non-operative management of gunshot wounds to the lumbosacral spine. Studies were evaluated for degree of neurologic improvement, complications, and antibiotic usage. An odds ratio and 95% confidence interval were calculated for dichotomous outcomes which were then pooled by random-effects model meta-analysis. Results: Five studies were included that met inclusion criteria. The total rate of neurologic improvement was 72.3% following surgical intervention and 61.7% following non-operative intervention. A random-effects model meta-analysis was carried out which failed to show a statistically significant difference in the rate of neurologic improvement between surgical and non-operative intervention (OR 1.07; 95% CI 0.45, 2.53; P = 0.88). In civilian only studies, a random-effects model meta-analysis failed to show a statistically significant difference in the rate of neurologic improvement between surgical and non-operative intervention (OR 0.75; 95% CI 0.21, 2.72; P = 0.66). Meta-analysis further failed to show a statistically significant difference in the rate of neurologic improvement between patients with either complete (OR 4.13; 95% CI 0.55, 30.80; P = 0.17) or incomplete (OR 0.38; 95% CI 0.10, 1.52; P = 0.17) neurologic injuries who underwent surgical and non-operative intervention. There were no significant differences in the number of infections and other complications between patients who underwent surgical and non-operative intervention. Conclusions: There were no statistically significant differences in the rate of neurologic improvement between those who underwent surgical or non-operative intervention. Further research is necessary to determine if surgical intervention for gunshot wounds to the lumbosacral spine, including in the case of retained bullet within the spinal canal, is efficacious.

scholarly journals A Point-Mass Mixture Random Effects Model for Pitching Metrics

2010 ◽  
Vol 6 (3) ◽  
Author(s):  
James Piette ◽  
Alexander Braunstein ◽  
Blakeley B McShane ◽  
Shane T. Jensen
Keyword(s):  
Random Effects ◽  
Point Mass ◽  
Random Effects Model
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