Looking for twins: how to build better counterfactuals with matching

2021 ◽  
pp. 1-16
Author(s):  
Stefano Costalli ◽  
Fedra Negri
Keyword(s):  
Observational Data ◽  
Selection Bias ◽  
Empirical Distribution ◽  
Exact Matching ◽  
Control Groups ◽  
Units Of Analysis ◽  
Pre Treatment ◽  
Peacekeeping Missions ◽  
And Control ◽  
Matching Techniques

Abstract A primary challenge for researchers that make use of observational data is selection bias (i.e. the units of analysis exhibit systematic differences and dis-homogeneities due to non-random selection into treatment). This article encourages researchers in acknowledging this problem and discusses how and – more importantly – under which assumptions they may resort to statistical matching techniques to reduce the imbalance in the empirical distribution of pre-treatment observable variables between the treatment and control groups. With the aim of providing a practical guidance, the article engages with the evaluation of the effectiveness of peacekeeping missions in the case of the Bosnian civil war, a research topic in which selection bias is a structural feature of the observational data researchers have to use, and shows how to apply the Coarsened Exact Matching (CEM), the most widely used matching algorithm in the fields of Political Science and International Relations.

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 Comparative studies of early season moxidectin treatment and conventional ivermectin/ benzimidazole treatments in the control of cyathostomes in horses

2012 ◽  
Vol 48 (No. 1 - 2) ◽  
pp. 9-17
Author(s):  
I. Langrová ◽  
I. Jankovská ◽  
M. Borovský
Keyword(s):  
Live Weight ◽  
Treated Group ◽  
Control Group ◽  
Control Groups ◽  
Grazing Period ◽  
The Mean ◽  
Faecal Egg Counts ◽  
Pre Treatment ◽  
And Control ◽  
First Time

Moxidectin administered in January or February at a single dose was tested for efficacy in horses on two farms for 12 and 11 months, respectively. Horses were infected with cyathostomes naturally in the previous grazing period. Forty horses of farm 1 and 20 horses of farm 2 were used in controlled tests to evaluate the efficacy of moxidectin 2% gel formulation at the dosage 0.4 mg moxidectin per kg of live weight, ivermectin commercial paste formulation at the dosage 0.2 mg ivermectin per kg of live weight, mebendazole and fenbendazole commercial paste formulation at the dosage both 7.5 mg mebendazole and fenbendazole per kg of live weight, all applied orally. Three control groups of 10 horses each (farm 1) were treated twice a year with ivermectin and benzimidazoles, respectively. Individual faecal egg counts, faecal cultures and larval differentiation were performed. Moxidectin had more prolonged and greater suppressive effects on the post-treatment reappearance and magnitude of strongyle egg counts than did ivermectin or benzimidazoles. In the moxidectin treated group (M1) strongyle eggs were seen for the first time in April and a slight increase in the mean count of eggs per gram of faeces (EPG) was observed during the rest of the season. Litter larval counts significantly reflected levels of exposure during the tested season. Twenty animals of farm 2 were allocated into two groups of ten horses each based on pre-treatment eggs per gram (EPG) counts (moxidectin treated group and control group). In the moxidectin treated group mean egg counts remained very low throughout the study. A plateau was reached by autumn, with egg counts ranging from 74 to 145 EPG. The faecal egg counts of moxidectin treated group (M2) were significantly higher in March, April, May and June.

Conjugated Linoleic Acid Causes a Marked Increase in Liver α-Tocopherol and Liver α-Tocopherol Transfer Protein in C57BL/6 J Mice

2010 ◽  
Vol 80 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Pei-Min Chao ◽  
Wan-Hsuan Chen ◽  
Chun-Huei Liao ◽  
Huey-Mei Shaw
Keyword(s):  
Antioxidant Enzymes ◽  
Linoleic Acid ◽  
Conjugated Linoleic Acid ◽  
Thiobarbituric Acid ◽  
Control Group ◽  
Thiobarbituric Acid Reactive Substances ◽  
Control Groups ◽  
Protein Levels ◽  
Transfer Protein ◽  
And Control

Conjugated linoleic acid (CLA) is a collective term for the positional and geometric isomers of a conjugated diene of linoleic acid (C18:2, n-6). The aims of the present study were to evaluate whether levels of hepatic α-tocopherol, α-tocopherol transfer protein (α-TTP), and antioxidant enzymes in mice were affected by a CLA-supplemented diet. C57BL/6 J mice were divided into the CLA and control groups, which were fed, respectively, a 5 % fat diet with or without 1 g/100 g of CLA (1:1 mixture of cis-9, trans-11 and trans-10, cis-12) for four weeks. α-Tocopherol levels in plasma and liver were significantly higher in the CLA group than in the control group. Liver α-TTP levels were also significantly increased in the CLA group, the α-TTP/β-actin ratio being 2.5-fold higher than that in control mice (p<0.01). Thiobarbituric acid-reactive substances were significantly decreased in the CLA group (p<0.01). There were no significant differences between the two groups in levels of three antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and catalase). The accumulation of liver α-tocopherol seen with the CLA diet can be attributed to the antioxidant potential of CLA and the ability of α-TTP induction. The lack of changes in antioxidant enzyme protein levels and the reduced lipid peroxidation in the liver of CLA mice are due to α-tocopherol accumulation.

The Prospects and Risks Connected with Increasing the Level of Self-Organisation in Students

2020 ◽  
pp. 75-81
Author(s):  
Svetlana Alexandrovna Kosareva ◽  
Keyword(s):  
Higher Education ◽  
Professional Competence ◽  
Initial Level ◽  
Education Institution ◽  
Diagnostic Methods ◽  
Study Guide ◽  
Learning Approaches ◽  
Control Groups ◽  
Self Organisation ◽  
And Control

The paper describes the method for increasing the level of self-organisation in students which has been developed by the author. It also contains the method testing results and presents the prospects and risks teachers could face while applying the method in a higher education institution. The purpose of this study is to find out the prospects and risks of applying the method for increasing the level of self-organisation in students and to determine the ways of reducing the risks. Methodology. The author points out the learning approaches which were the basis of developing the method and describes diagnostic methods for determining students’ self-organisation levels. The work focused on increasing each student’s initial level consists of a theoretical and a practical part and includes project activities on creating a study guide. The results of the study. The method developed proved to be effective. It was established by diagnosing the final level of self-organisation in students in the experimental and control groups. The paper considers the advantages of the method among which there is universal character, flexibility, improvements to teacher’s and students’ professional competence, etc. At the same time it is necessary to be aware of the risks due to the increased amount of teacher’s work and the fact that students’ work within the project tends to be monotonous. In conclusion, the prospects of the method for increasing the level of self-organisation in students are related to its advantages and the final results of the work. The risks of its use can be reduced with the help of the measures proposed in the paper.

Sri Lankan Cleft Lip and Palate Study Model Analysis: Clefts of the Secondary Palate

1993 ◽  
Vol 30 (2) ◽  
pp. 227-230 ◽  
Author(s):  
Andrew Mccance ◽  
David Roberts-Harry ◽  
Martyn Sherriff ◽  
Michael Mars ◽  
William J.B. Houston
Keyword(s):  
Cleft Lip ◽  
Cleft Lip And Palate ◽  
Model Analysis ◽  
Control Group ◽  
Tooth Size ◽  
Sri Lankan ◽  
Control Groups ◽  
Secondary Palate ◽  
Comparable Control ◽  
And Control

The study models of a group of adult Sri Lankan patients with clefts of the secondary palate were investigated. Tooth-size and arch-dimension comparisons were made with a comparable control group. Significant differences were found between the cleft and control groups in tooth sizes, chord lengths, and arch widths. The cleft group dimensions were generally smaller than those of the control group. Overjets were larger in the cleft group.

THE EFFECT OF APPLYING ANIMAL CARTOON PICTURES ON STUDENTS’ ACHIEVEMENT IN WRITING NARRATIVE TEXT

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Hasanul Arifin Zul And Masitowarni Siregar
Keyword(s):  
T Test ◽  
Narrative Text ◽  
Control Group ◽  
First Year ◽  
Writing Achievement ◽  
Control Groups ◽  
Post Test ◽  
Written Test ◽  
And Control ◽  
Experimental Group

This thesis is focused on the investigation of the effect of applying animal cartoon pictures on students’ achievement in writing narrative text. This study aims to find whether applying animal cartoon pictures significantly affect the students’ writing achievement or not. The data in this study were obtained by administering a written test. The population was the 2015/2016 first year (grade XI) of SMA Swasta Nusantara Lubuk Pakam and 66 students were taken as the sample by using random sampling. The sample was divided into two groups, experimental and control groups. The experimental group was taught by applying animal cartoon pictures while the control group without animal cartoon pictures (x = lecturing). The data were taken the scores from the pre-test and post-test to both experimental and control groups. These data were analyzed by using t-test. The result of computing the t-test obviously showed that t-observed is higher than t-table (5.21 >1,67) with the degree of freedom 64 (df =N-2) at the level significance 0,05 one tail test. It showed that the application of animal cartoon pictures significantly affected the students of SMA Swasta Nusantara Lubuk Pakam achievement in writing narrative text.

THE EFFECT OF APPLYING DEMONSTRATION METHOD ON STUDENTS’ ACHIEVEMENT IN SPEAKING SKILL AT THE THIRD GRADE OF SMK PAB 3 MEDAN ESTATE

2015 ◽  
Vol 4 (2) ◽  
Author(s):  
Meryanti Napitupulu And Anni Holila Pulungan
Keyword(s):  
High School ◽  
Control Group ◽  
Vocational High School ◽  
Control Groups ◽  
Speaking Test ◽  
The Third ◽  
Speaking Skill ◽  
The Subject ◽  
And Control ◽  
Experimental Group

This study was conducted as an attempt to discover the effect of applying Demonstration Method on students’ achievement in speaking skill. It was an experimental research. The subject was students of Grade XII, Vocational High School (Sekolah Menengah Kejuruan: SMK), which consisted of 79 students. The research was divided into two groups: experimental and control groups. The instrument used to collect the data was speaking test. To obtain the reliability of the test, the writer applied Kuder Richardson 21 formula. The result of the reliability was 0.7, and it was found that the test was reliable. The data were analyzed by using t-test formula. The analysis showed that the scores of the students in the experimental group were significantly higher than the scores of the students in the control group at the level of significant m = 0.05 with the degree of freedom (df) 77, t-observed value 8.9 > t-table value 1.99. The findings indicate that using Demonstration Method significantly affected the students’ achievement in speaking skill. So, English teachers are suggested to use Demonstration Method in order to improve students’ achievement in speaking skill.

Effects of Virgin Coconut Oil as Adjunct Therapy in the Treatment of Allergic Rhinitis

2016 ◽  
Vol 1 (1) ◽  
pp. 22
Author(s):  
Nazli Zainuddin ◽  
Nurul Azira Mohd Shah ◽  
Rosdan Salim
Keyword(s):  
Allergic Rhinitis ◽  
Side Effects ◽  
Coconut Oil ◽  
Test Group ◽  
Nasal Symptom ◽  
Control Group ◽  
Virgin Coconut Oil ◽  
Control Groups ◽  
Significant Difference ◽  
And Control

Introduction: The role of virgin coconut oil in the treatment of allergic rhinitis is controversial. Thus, the aim of the present study is to determine the effects of virgin coconut oil ingestion, in addition to standard medications, on allergic rhinitis. We also studied the side effects of consumption of virgin coconut oil. Methods: Fifty two subjects were equally divided into test and control groups. All subjects received a daily dose of 10mg of loratadine for 28 days. The test group was given 10ml of virgin coconut oil three times a day in addition to loratadine. The symptoms of allergic rhinitis were scored at the beginning and end of the study. Results:, the symptom score were divided into nasal and non-nasal symptom scores. Sneezing score showed a significant difference, however the score was more in control group than test group, indicating that improvement in symptom was more in control group. The rest of the nasal symptom and non-nasal symptom score showed no significant difference between test and control groups. Approximately 58% of the test subjects developed side effects from consumption of virgin coconut oil, mainly gastrointestinal side effects. Conclusion: In the present study, ingestion of virgin coconut oil does not improve the overall and individual symptoms of allergic rhinitis, furthermore it has side effects.

Effects of Time and Perceptual Orientation on Actors' and Observers' Attributions

1984 ◽  
Vol 58 (1) ◽  
pp. 23-30
Author(s):  
Donald S. Martin ◽  
Ming-Shiunn Huang
Keyword(s):  
Video Recording ◽  
Control Group ◽  
Control Groups ◽  
Video Recordings ◽  
Before And After ◽  
Perceptual Orientation ◽  
Initial Difference ◽  
Variety Show ◽  
And Control ◽  
Unrelated Variety

The actor/observer effect was examined by Storms in a 1973 study which manipulated perceptual orientation using video recordings. Storms' study was complex and some of his results equivocal. The present study attempted to recreate the perceptual reorientation effect using a simplified experimental design and an initial difference between actors and observers which was the reverse of the original effect. Female undergraduates performed a motor co-ordination task as actors while watched by observers. Each person made attributions for the actor's behaviour before and after watching a video recording of the performance. For a control group the video recording was of an unrelated variety show excerpt. Actors' initial attributions were less situational than observers'. Both actors and observers became more situational after the video replay but this effect occurred in both experimental and control groups. It was suggested the passage of time between first and second recording of attributions could account for the findings and care should be taken when interpreting Storms' (1973) study and others which did not adequately control for temporal effects.

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