Bootstrap Confidence Intervals and Coverage Probabilities of Regression Parameter Estimates Using Trimmed Elemental Estimation

Mayo and Gray introduced the leverage residual-weighted elemental (LRWE) classification of regression estimators and a new method of estimation called trimmed elemental estimation (TEE), showing the efficiency and robustness of TEE point estimates. Using bootstrap methods, properties of various trimmed elemental estimator interval estimates to allow for inference are examined and estimates with ordinary least squares (OLS) and least sum of absolute values (LAV) are compared. Confidence intervals and coverage probabilities for the estimators using a variety of error distributions, sample sizes, and number of parameters are examined. To reduce computational intensity, randomly selecting elemental subsets to calculate the parameter estimates were investigated. For the distributions considered, randomly selecting 50% of the elemental regressions led to highly accurate estimates

JMASM43: TEEReg: Trimmed Elemental Estimation (R)

Trimmed elemental regression is robust to outliers and violations of model assumptions. Its properties and statistical inference were evaluated using bias-corrected and accelerated bootstrap confidence intervals. An R package named TEEReg is developed to compute the trimmed elemental estimates and the corresponding bootstrap confidence intervals. Two examples are provided to demonstrate its usage

Generalized Linear Mixed-Effects Models for the Analysis of Odor Detection Data

Olfactory detection has become a science of interest. Seven individuals’ odor detection abilities are explored and an attempt is made to characterize all subjects with one generalized linear mixed effects model. Two methods of fitting the models were used and simulations were conducted to discover which method yielded the best results

Adherence to Principles of Motivational Interviewing and Client Within-Session Behavior

The purpose of this study was to examine whether counselor adherence to Motivational Interviewing (MI) principles was associated with more productive within-session client behavior in a smoking cessation trial for African American smokers. For these analyses 89 baseline counseling sessions of the trial were audiotaped and coded using the Motivational Interviewing Skill Code (MISC). Counselor adherence indicators included a global subjective rating of MI adherence and the frequency of MI-consistent and MI-inconsistent counselor behaviors described in the MISC. Indicators of productive client behaviors included global subjective ratings of within-session client functioning and counselor-client interaction, as well as the frequency of statements by the client favorable toward changing behavior (“change talk”) and resistant regarding changing behavior (“resist-change talk”). Results provided support for the principles of MI. Counselor adherence indexed by both the global subjective rating and MI-consistent behavior frequency was significantly positively associated with global ratings of within-session client functioning and counselor-client interaction, as well as more change talk

Bayesian accrual prediction for interim review of clinical studies: open source R package and smartphone application

Illustration of use of R accrual package. (DOCX 917 kb

A Randomized, Controlled, Supervised, Excerise Trial in Young Overweight Men and Women: The Midwest Exercise Trial II (MET2)

We evaluated weight loss response to 16 months of supervised exercise (45 minutes/d, 5 d/wk, 75% heart-rate-reserve) in sedentary, overweight/obese participants without energy restriction in the Midwest Exercise Trial (MET1). Results indicated men lost weight, women did not. The gender differences were associated with differences in the energy expenditure of exercise (EEEx) (men = 667 ± 116; women = 439 ± 88 kcal/session) when exercise was prescribed by frequency, intensity and duration. MET2 is a randomized control trial designed and powered to examine differences in weight loss and gender in response to EEEx for men and women of 400 or 600 kcal/session, 5d/wk, for 10 months without energy restriction. One hundred forty one participants will be randomized to 1 of 2 exercise groups or a non-exercise control. EEEx will be verified by indirect calorimetry monthly during the intervention. This study will evaluate: (1) the weight change response to two levels of EEEx versus non-exercise control; (2) gender differences in weight response to two levels of EEEx; (3) potential compensatory changes in energy intake and/or daily physical activity that may explain the observed weight changes. Results from this study may impact how exercise is prescribed for weight loss and prevention of weight regain and may clarify if men and women differ in response to exercise