Instrumental Variables: A Simpleminded Introduction

2007 ◽  
Author(s):  
Bernard S. Black
Keyword(s):  
Instrumental Variables

scholarly journals Optimizing Transmit Sequence and Instrumental Variables Receiver for Dual-Function Complexity System

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yu Yao ◽  
Junhui Zhao ◽  
Lenan Wu
Keyword(s):  
Approximate Solution ◽  
Instrumental Variables ◽  
Performance Index ◽  
Dual Function ◽  
Np Hard ◽  
Match Filter ◽  
Filter Output ◽  
Phase Code ◽  
Discrete Phase ◽  
Simulation Results

This correspondence deals with the joint cognitive design of transmit coded sequences and instrumental variables (IV) receive filter to enhance the performance of a dual-function radar-communication (DFRC) system in the presence of clutter disturbance. The IV receiver can reject clutter more efficiently than the match filter. The signal-to-clutter-and-noise ratio (SCNR) of the IV filter output is viewed as the performance index of the complexity system. We focus on phase only sequences, sharing both a continuous and a discrete phase code and develop optimization algorithms to achieve reasonable pairs of transmit coded sequences and IV receiver that fine approximate the behavior of the optimum SCNR. All iterations involve the solution of NP-hard quadratic fractional problems. The relaxation plus randomization technique is used to find an approximate solution. The complexity, corresponding to the operation of the proposed algorithms, depends on the number of acceptable iterations along with on and the complexity involved in all iterations. Simulation results are offered to evaluate the performance generated by the proposed scheme.

Does Board Independence Increase Firm Value? Evidence from Closed-End Funds

2019 ◽  
pp. 1-24
Author(s):  
Matthew E. Souther
Keyword(s):  
Instrumental Variables ◽  
Firm Value ◽  
Board Independence ◽  
Difference In Differences ◽  
Cross Sectional ◽  
Closed End Funds ◽  
The Impact ◽  
New Evidence

Researchers disagree about the impact of board independence on firm value. The disagreement generally stems from the endogenous nature of board appointments. I add new evidence to this discussion by using a sample of closed-end funds to document the value-enhancing effects of independent boards. Using cross-sectional, difference-in-differences, and instrumental variables techniques, I address these endogeneity concerns and find consistent evidence that board independence is associated with higher firm value.

The determinants of the intensity of home-based informal care among cancer patients in receipt of home-based palliative care

2020 ◽  
pp. 026921632097927
Author(s):  
Jiaoli Cai ◽  
Li Zhang ◽  
Denise Guerriere ◽  
Peter C Coyte
Keyword(s):  
Palliative Care ◽  
Marital Status ◽  
Cancer Patients ◽  
Informal Care ◽  
Instrumental Variables ◽  
Spousal Caregivers ◽  
Living Alone ◽  
Policy Makers ◽  
Cohort Design ◽  
Home Based

Background: Understanding the determinants of the intensity of informal care may assist policy makers in the identification of supports for informal caregivers. Little is known about the utilization of informal care throughout the palliative care trajectory. Aim: The purpose of this study was to analyze the intensity and determinants of the use of informal care among cancer patients over the palliative care trajectory. Design: This was a longitudinal, prospective cohort design conducted in Canada. Regression analysis using instrumental variables was applied. Setting/participants: From November 2013 to August 2017, a total of 273 caregivers of cancer patients were interviewed biweekly over the course of the care recipient’s palliative care trajectory. The outcome was the number of hours of informal care provided by unpaid caregivers, that is, hours of informal care. Results: The number of hours of informal care increased as patients approached death. Home-based nursing care complemented, and hence, increased the provision of informal care. Patients living alone and caregivers who were employed were associated with the provision of fewer hours of informal care. Spousal caregivers provided more hours of informal care. Patient’s age, sex, and marital status, and caregiver’s age, sex, marital status, and education were associated with the number of hours of informal care. Conclusions: The intensity of informal care was determined by predisposing, enabling, and needs-based factors. This study provides a reference for the planning and targeting of supports for the provision of informal care.

scholarly journals Causal Association between Periodontitis and Parkinson’s Disease: A Bidirectional Mendelian Randomization Study

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 772
Author(s):  
João Botelho ◽  
Vanessa Machado ◽  
José João Mendes ◽  
Paulo Mascarenhas
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Instrumental Variables ◽  
Mendelian Randomization ◽  
Association Studies ◽  
European Ancestry ◽  
Genome Wide Association Studies ◽  
Nucleotide Polymorphisms ◽  
Genetic Liability ◽  
Bidirectional Association

The latest evidence revealed a possible association between periodontitis and Parkinson’s disease (PD). We explored the causal relationship of this bidirectional association through two-sample Mendelian randomization (MR) in European ancestry populations. To this end, we used openly accessible data of genome-wide association studies (GWAS) on periodontitis and PD. As instrumental variables for periodontitis, seventeen single-nucleotide polymorphisms (SNPs) from a GWAS of periodontitis (1817 periodontitis cases vs. 2215 controls) and eight non-overlapping SNPs of periodontitis from an additional GWAS for validation purposes. Instrumental variables to explore for the reverse causation included forty-five SNPs from a GWAS of PD (20,184 cases and 397,324 controls). Multiple approaches of MR were carried-out. There was no evidence of genetic liability of periodontitis being associated with a higher risk of PD (B = −0.0003, Standard Error [SE] 0.0003, p = 0.26). The eight independent SNPs (B = −0.0000, SE 0.0001, p = 0.99) validated this outcome. We also found no association of genetically primed PD towards periodontitis (B = −0.0001, SE 0.0001, p = 0.19). These MR study findings do not support a bidirectional causal genetic liability between periodontitis and PD. Further GWAS studies are needed to confirm the consistency of these results.

scholarly journals Postoperative non-steroidal anti-inflammatory drug use and oncological outcomes of rectal cancer

BJS Open ◽  
2021 ◽  
Vol 5 (1) ◽  
Author(s):  
O Grahn ◽  
M Lundin ◽  
M-L Lydrup ◽  
E Angenete ◽  
M Rutegård
Keyword(s):  
Rectal Cancer ◽  
Propensity Score ◽  
Propensity Score Matching ◽  
Instrumental Variables ◽  
Cox Regression ◽  
Recurrence Free Survival ◽  
Free Survival ◽  
Oncological Outcomes ◽  
Anti Inflammatory ◽  
Instrumental Variables Approach

Abstract Background Non-steroidal anti-inflammatory drugs (NSAIDs) are known to suppress the inflammatory response after surgery and are often used for pain control. This study aimed to investigate NSAID use after radical surgical resection for rectal cancer and long-term oncological outcomes. Methods A cohort of patients who underwent anterior resection for rectal cancer between 2007 and 2013 in 15 hospitals in Sweden was investigated retrospectively. Data were obtained from the Swedish Colorectal Cancer Registry and medical records; follow-up was undertaken until July 2019. Patients who received NSAID treatment for at least 2 days after surgery were compared with controls who did not, and the primary outcome was recurrence-free survival. Cox regression modelling with confounder adjustment, propensity score matching, and an instrumental variables approach were used; missing data were handled by multiple imputation. Results The cohort included 1341 patients, 362 (27.0 per cent) of whom received NSAIDs after operation. In analyses using conventional regression and propensity score matching, there was no significant association between postoperative NSAID use and recurrence-free survival (adjusted hazard ratio (HR) 1.02, 0.79 to 1.33). The instrumental variables approach, including individual hospital as the instrumental variable and clinicopathological variables as co-variables, suggested a potential improvement in the NSAID group (HR 0.61, 0.38 to 0.99). Conclusion Conventional modelling did not demonstrate an association between postoperative NSAID use and recurrence-free survival in patients with rectal cancer, although an instrumental variables approach suggested a potential benefit.

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