scholarly journals Lasso adjustments of treatment effect estimates in randomized experiments

2016 ◽  
Vol 113 (27) ◽  
pp. 7383-7390 ◽  
Author(s):  
Adam Bloniarz ◽  
Hanzhong Liu ◽  
Cun-Hui Zhang ◽  
Jasjeet S. Sekhon ◽  
Bin Yu
Keyword(s):  
Treatment Effect ◽  
Multivariate Regression ◽  
Asymptotic Variance ◽  
Ordinary Least Squares ◽  
Randomized Experiments ◽  
Control Groups ◽  
The Difference ◽  
Selection Operator ◽  
Simple Difference ◽  
And Control

We provide a principled way for investigators to analyze randomized experiments when the number of covariates is large. Investigators often use linear multivariate regression to analyze randomized experiments instead of simply reporting the difference of means between treatment and control groups. Their aim is to reduce the variance of the estimated treatment effect by adjusting for covariates. If there are a large number of covariates relative to the number of observations, regression may perform poorly because of overfitting. In such cases, the least absolute shrinkage and selection operator (Lasso) may be helpful. We study the resulting Lasso-based treatment effect estimator under the Neyman–Rubin model of randomized experiments. We present theoretical conditions that guarantee that the estimator is more efficient than the simple difference-of-means estimator, and we provide a conservative estimator of the asymptotic variance, which can yield tighter confidence intervals than the difference-of-means estimator. Simulation and data examples show that Lasso-based adjustment can be advantageous even when the number of covariates is less than the number of observations. Specifically, a variant using Lasso for selection and ordinary least squares (OLS) for estimation performs particularly well, and it chooses a smoothing parameter based on combined performance of Lasso and OLS.

scholarly journals Regression-adjusted average treatment effect estimates in stratified randomized experiments

Biometrika ◽  
2020 ◽  
Vol 107 (4) ◽  
pp. 935-948
Author(s):  
Hanzhong Liu ◽  
Yuehan Yang
Keyword(s):  
Treatment Effect ◽  
Asymptotic Variance ◽  
Average Treatment Effect ◽  
Randomized Experiments ◽  
Asymptotically Normal ◽  
Variance Estimators ◽  
Average Treatment ◽  
Effect Estimation ◽  
Regression Adjustment ◽  
And Control

Summary Linear regression is often used in the analysis of randomized experiments to improve treatment effect estimation by adjusting for imbalances of covariates in the treatment and control groups. This article proposes a randomization-based inference framework for regression adjustment in stratified randomized experiments. We re-establish, under mild conditions, the finite-population central limit theorem for a stratified experiment, and we prove that both the stratified difference-in-means estimator and the regression-adjusted average treatment effect estimator are consistent and asymptotically normal; the asymptotic variance of the latter is no greater and typically less than that of the former. We also provide conservative variance estimators that can be used to construct large-sample confidence intervals for the average treatment effect.

scholarly journals The effect of diminazene aceturate on cholinesterase activity in dogs with canine babesiosis

1997 ◽  
Vol 68 (4) ◽  
Author(s):  
R.J. Milner ◽  
F. Reyers ◽  
J.H. Taylor ◽  
J.S. Van den Berg
Keyword(s):  
Treatment Group ◽  
Underlying Mechanism ◽  
Time Interval ◽  
Control Groups ◽  
Canine Babesiosis ◽  
Diminazene Aceturate ◽  
Time Intervals ◽  
Significant Depression ◽  
The Difference ◽  
And Control

A clinical trial was designed to evaluate the effects of diminazene aceturate and its stabiliser antipyrine on serum pseudocholinesterase (PChE) and red blood cell acetylcholinesterase (RBC AChE) in dogs with babesiosis. The trial was conducted on naturally occurring, uncomplicated cases of babesiosis (n = 20) that were randomly allocated to groups receiving a standard therapeutic dose of diminazene aceturate with antipyrine stabiliser (n = 10) or antipyrine alone (n = 10). Blood was drawn immediately before and every 15 minutes for 1 hour after treatment. Plasma PChE showed a 4 % decrease between 0 and 60 min within the treatment group (p < 0.05). No statistically significant differences were found between the treatment and control groups at any of the time intervals for PChE. There was an increase in RBC AChE activity at 15 min in the treatment group (p < 0.05). No significant differences were found between the treatment and control groups at any time interval for RBC AChE. In view of the difference in PChE, samples from additional, new cases (n = 10) of canine babesiosis were collected to identify the affect of the drug over 12 hours. No significant depression was identified over this time interval. The results suggests that the underlying mechanism in producing side-effects, when they do occur, is unlikely to be through cholinesterase depression.

scholarly journals Effects of two different deep digital flexor tenotomy techniques on distal articular angles of equine cadaver forelimbs

2012 ◽  
Vol 42 (11) ◽  
pp. 2005-2010
Author(s):  
Antonio Cezar de Oliveira Dearo ◽  
Vitor Bruno Bianconi Rosa ◽  
Peter Reichmann ◽  
Milton Luis Ribeiro de Oliveira
Keyword(s):  
Quantitative Data ◽  
Statistical Significance ◽  
Surgical Approaches ◽  
Control Groups ◽  
Before And After ◽  
Distal Interphalangeal ◽  
The Difference ◽  
And Control ◽  
Flexor Tenotomy

Deep digital flexor (DDF) tenotomy is a technique employed for years to treat selected disorders of the musculoskeletal system in horses. Although two different surgical approaches (i.e. mid-metacarpal and pastern) have been described for performing the procedure, in vitro quantitative data regarding the modifications induced by either technique on the distal articular angles is lacking. Therefore, the purpose of the study reported here was to investigate the viability of a proposed biomechanical system of induced-traction used to compare the two DDF tenotomy techniques by measuring the distal articular angles of equine cadaver forelimbs. Ten pairs of forelimbs were collected and mounted to a biomechanical system developed to apply traction at the toe level. Dorsal articular angles of the metacarpophalangeal (MP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints were determined by geometric lines on radiographs taken before and after performing each technique. Comparisons between each tenotomy group and its own control, for each joint, and between the two tenotomy groups using as variable the difference between the tenotomy and control groups were tested. Despite the lack of statistical significance, the DDF tenotomy technique at the pastern level produced extension, to a lesser and greater extent, of the PIP and DIP joints, respectively when compared to the mid-metacarpal level. No remarkable differences could be observed for the MP joint. The developed traction-induced biomechanical construct seemed to be effective in producing valuable quantitative estimations of the distal articular angles of equine cadaver forelimbs subjected to different DDF tenotomy techniques.

scholarly journals A study on association of polymorphisms in calpain10 and TCF7l2 genes with type 2 diabetes mellitus

Genetika ◽  
2015 ◽  
Vol 47 (1) ◽  
pp. 161-170 ◽  
Author(s):  
Maryam Rezazadeh ◽  
Nasim Sohrabifar ◽  
Hossein Jafari ◽  
Ardabili Mohaddes ◽  
Jalal Gharesouran
Keyword(s):  
Type 2 Diabetes ◽  
Allelic Association ◽  
Diabetic Patients ◽  
Control Groups ◽  
Type2 Diabetes ◽  
North Of Iran ◽  
Calpain 10 ◽  
The Difference ◽  
And Control

Polymorphisms of the Calpain10 and TCF7L2 genes were identified as possible type 2 diabetes susceptibility genetic markers. We conducted a case-control study to evaluate the relation between SNP43 of calpain-10 and rs12255372 and rs7903146 in the TCF7L2 with type2 diabetes in western-north of Iran. The role of these variants in Iranian population was less clear. A total of 202 patients and healthy controls were enrolled to analysis the frequency distribution of Calpain10 and TCF7L2 polymorphisms (SNP43, rs12255372 and rs7903146) using polymerase chain reaction-restriction fragment length polymorphism (PCR - RFLP) method. The frequency of allele A in controls was significantly greater than that of diabetic patients (P=0.031), whereas the difference between distribution of SNP43 genotypes (A/A, A/G, G/G) were non- significant in case and control groups. Non significant association was also observed between G/G, A/G or A/A genotypes and type 2 Diabetes. The frequency of the ?T? allele of rs12255372 (G/T) was significantly associated with type 2 diabetes (OR= 0.55, 95% confidence interval [CI], 1.11-1.51; P<0.001). No allelic association was found for rs7903146(C/T) polymorphism. The distribution of alleles in case and control groups are significantly different indicating the G allele is associated with type 2 diabetes. The rs12255372 (G/T) may be associated with type 2 diabetes.

scholarly journals Measuring the sensitivity of difference-in-difference estimates to the parallel trends assumption

2021 ◽  
pp. 263208432110613
Author(s):  
Landon Gibson ◽  
Frederick Zimmerman
Keyword(s):  
Sensitivity Analysis ◽  
Treatment Period ◽  
Treatment Effect ◽  
Statistical Tests ◽  
Sensitivity Analyses ◽  
Difference In Difference ◽  
Control Groups ◽  
Pre Treatment ◽  
Background Difference ◽  
And Control

Background. Difference-in-Difference makes a critical assumption that the changes in the outcomes, over the post-treatment period, are similar between the treated and control groups—the parallel trends assumption. Evaluation of this assumption is often done either by graphical examination or by statistical tests in the pre-treatment period. They result in a binary conclusion about the validity of the assumption. Purpose. This paper proposes a sensitivity analysis that quantifies the departure from parallel trends necessary to meaningfully change the estimated treatment effect. Results. Sensitivity analyses have an advantage over traditional parallel trends tests: they use all available data and thereby work even if only one pre-period is available, and they quantify the strength of unobserved confounder(s) required to change the conclusions of a study. Conclusions. We apply the sensitivity analysis metrics developed by Cinelli and Hazlett (2020) and illustrate them on two studies.

scholarly journals Effect of iRoot BP Plus Pulpotomy for Immediate Repair in Children with Young Permanent Teeth Crown Fracture

2020 ◽  
Vol 4 (2) ◽  
Author(s):  
Jiaying Song
Keyword(s):  
Success Rate ◽  
Clinical Effect ◽  
Permanent Teeth ◽  
Control Group ◽  
Observation Group ◽  
Control Groups ◽  
Before And After ◽  
Random Number Table ◽  
The Difference ◽  
And Control

Objective: To explore the clinical effect of iRoot BP Plus pulpotomy for immediate repair in children with young permanent teeth crown fracture. Methods: From September 2017 to October 2018, 80 children (80 affected teeth) with young permanent teeth crown fracture who treated in the hospital were selected as the research objects. Random number table method was used to divide them into observation and control groups with each group of forty patients (40 affected teeth). The children in the control group were treated with calcium hydroxide resin, while the observation group were treated with iRoot BP Plus for immediate repair. The surgical success rate was compared between the two groups, and the pulp vitality before and after treatment were compared. Results: At 3 months and 6 months after surgery, the success rate of children in the observation group was higher than that in the control group, and the difference was statistically significant (P<0.05). The percentage of children with negative pulp activity in the observation group was higher than that in the control group, and the difference was statistically significant (P<0.05). Conclusion: Immediate repair with iRoot BP Plus pulpotomy in children with young permanent teeth crown fracture has significant clinical effect.

Auditory and Visual Executive Functions in Children and Response to Methylphenidate: A Randomized Controlled Trial

2017 ◽  
Vol 24 (2) ◽  
pp. 235-245
Author(s):  
Yaffa Hadar ◽  
Shraga Hocherman ◽  
Oren Lamm ◽  
Emanuel Tirosh
Keyword(s):  
Executive Functions ◽  
Visual Cues ◽  
Controlled Trial ◽  
Crossover Design ◽  
Control Groups ◽  
Children With Adhd ◽  
Randomized Controlled ◽  
The Difference ◽  
Visually Based ◽  
And Control

Objectives: The aim of the study was to assess auditory and visually based executive functions (EFs) and the effect of methylphenidate (MPH) in children with ADHD. Methods: Thirty-six boys between the ages of 8.3 and 9.7 years with ADHD and 36 matched controls were included. The study group was randomized into MPH and placebo for 7 days each in a crossover design. A Cued Choice Reaction Time (CCRT) test that included incongruent cuing was administered at baseline and following 1 and 2 weeks. Results: The difference between the study and control groups was more evident with visual cues and incongruent cuing. Increased gains by children with predominantly hyperactive–impulsive\combined (HI\C) type of ADHD were observed under MPH. Conclusions: The differences between children with ADHD and typical children are more pronounce under incongruent auditory cuing . The gains attributable to MPH are more specific to tasks involving auditory and visual EFs and in children with HI\C type ADHDs.

Effects of Mindfulness-Based Psychoeducation on the Internalized Stigmatization Level of Patients With Schizophrenia

2018 ◽  
Vol 29 (7) ◽  
pp. 496-503 ◽  
Author(s):  
Emine Yılmaz ◽  
Funda Kavak
Keyword(s):  
Health Centers ◽  
Control Group ◽  
Community Mental Health Centers ◽  
Control Groups ◽  
Face To Face ◽  
Significant Difference ◽  
The Difference ◽  
Mental Health Centers ◽  
And Control ◽  
Experimental Group

The aim of this study was to determine the effects of mindfulness-based psychoeducation on internalized stigma in patients with schizophrenia. The patients were recruited from the community mental health centers. This quasiexperimental study was conducted using pretests and posttests with a control group. The participants were 69 patients with schizophrenia; 34 were part of the experimental group and 35 were part of the control group. The patients in the experimental group participated 2 days a week for 6 weeks in a total of 12 sessions which were given in the form of face-to-face group training. The difference between the scale mean posttest scores of the patients in the experimental and control groups was found to be statistically significant ( p < .05). In the intragroup comparisons, a significant difference was found between the stigma mean scores in the experimental group ( p < .05). It was concluded that mindfulness-based psychoeducation was effective in reducing stigma in patients with schizophrenia.

Abstract 2211: Statin Therapy May Increase the Risk of Intracerebral Hemorrhage: A Meta-analysis of 26 Randomized Controlled Trials

Stroke ◽  
2012 ◽  
Vol 43 (suppl_1) ◽  
Author(s):  
James S McKinney ◽  
William J Kostis ◽  
John B Kostis
Keyword(s):  
Statin Therapy ◽  
Meta Analysis ◽  
Active Group ◽  
Controlled Trials ◽  
Control Groups ◽  
Randomized Controlled ◽  
All Cause Mortality ◽  
Group A ◽  
The Difference ◽  
And Control

Introduction--- Statin therapy decreases the risk of myocardial infarction and ischemic stroke. However, an increased risk of intracerebral hemorrhage (ICH) has been observed in some studies. To investigate this issue we performed a meta-analysis of all randomized controlled trials (RCTs) using statins that reported ICH. Methods--- We performed a Medline literature search through March 18, 2011 and identified additional RCTs by reviewing reference lists of retrieved studies and prior meta-analyses. All RCTs of statin therapy versus placebo or high dose versus low dose statin therapy that reported ICH or hemorrhagic stroke were included. The primary outcome variable was ICH. 26 RCTs were included. All analyses used random effects models and heterogeneity was not observed in any of the analyses. Results--- 84 831 subjects were included in the Active group, and 84 851 in the Control group. A trend towards a higher incidence of ICH was observed in the Active treatment group compared to Control (OR = 1.15; 95% CI = 0.91 to 1.45, p =0.24) (Figure). Significant relationships were not observed between the log OR for ICH with achieved LDL in the Active group (slope = 0.0002; 95% CI = -0.0098 to 0.0101, p =0.96) or with the difference in LDL drop between the Active and Control groups (slope = 0.0030; 95% CI = -0.0089 to 0.0149, p =0.62). Total stroke (OR = 0.84; 95% CI = 0.78 to 0.91, p <0.001) and all-cause mortality (OR = 0.91; 95% CI = 0.86 to 0.96, p <0.001) were significantly reduced in the Active group. A significant relationship between all-cause mortality and the difference in LDL drop between the Active and Control groups was observed (slope = -0.0030; 95% CI = -0.0009 to -0.0051, p<0.005). There was not evidence of publication bias in this meta-analysis. Conclusions--- Active therapy was associated with a trend towards increased ICH in this meta-analysis of 26 RCTs of statin therapy. However, this risk does not appear to be related to the degree of decline or achieved LDL. The risk of ICH is offset by a significant reduction in ischemic stroke and all-cause mortality and should not dissuade practitioners from prescribing statins in otherwise appropriate patients.

scholarly journals EFFECT OF 12.5% VIRGIN COCONUT OIL (COCOS NUCIFERA) MOUTHWASH ON PLAQUE INDEX OF FIXED PROSTHETIC DENTURE USERS

2018 ◽  
Vol 9 ◽  
pp. 41
Author(s):  
Leo Saputra ◽  
Farisza Gita ◽  
Ratna Sari Dewi
Keyword(s):  
Cocos Nucifera ◽  
Coconut Oil ◽  
Plaque Index ◽  
Control Groups ◽  
Index Measurement ◽  
Significant Difference ◽  
Before And After ◽  
The Difference ◽  
And Gender ◽  
And Control

Objective: To find out the difference in the plaque index scores of FPD users before and after using a 12.5% VCO mouthwash.Methods: The plaque index measurement of an abutment tooth was taken on 40 subjects with FPD in both test and control groups. Subjects used a 12.5% VCO mouthwash or aquades twice a day for 4 days after brushing their teeth. Statistical analysis of the measurement result of the plaque index scores before and after using the coconut oil mouthwash was done using the Wilcoxon test.Results: There is a statistically significant difference in the plaque index scores of FPD users before and after using the 12.5% VCO mouthwash with a statistically significant decrease in plaque index scores among restoration margin locations and tooth brushing habits, but not among age and gender groups.Conclusion: Using a 12.5% VCO mouthwash may decrease the plaque index of fixed prosthetic denture users.

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