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Related Concept Videos

Randomized Experiments01:13

Randomized Experiments

The randomization process involves assigning study participants randomly to experimental or control groups based on their probability of being equally assigned. Randomization is meant to eliminate selection bias and balance known and unknown confounding factors so that the control group is similar to the treatment group as much as possible. A computer program and a random number generator can be used to assign participants to groups in a way that minimizes bias.
Simple randomization
Simple...
Blinding01:11

Blinding

Blinding is a commonly used method of not telling participants which treatment a subject is receiving. Blinding is a critical part of a randomized control trial or RCT. It reduces the bias that affects the results. In an RCT, blinding is used in the form of a placebo. A placebo effect occurs when untreated subjects falsely believe they have received the treatment and report improved symptoms. A placebo or a dummy treatment is administered to subjects to negate the bias caused by such an effect.
Strategies for Assessing and Addressing Confounding01:25

Strategies for Assessing and Addressing Confounding

Confounding is a critical issue in epidemiological studies, often leading to misleading conclusions about associations between exposures and outcomes. It occurs when the relationship between the exposure and the outcome is mixed with the effects of other factors that influence the outcome. Given that, addressing confounding is of high importance for drawing accurate inferences in research.
Confounding can be addressed at both the design phase of a study and through analytical methods after data...
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches01:23

Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches

Biopharmaceutical studies constitute a vital field aiming to enhance drug delivery methods and refine therapeutic approaches, drawing upon diverse interdisciplinary knowledge. In research methodologies, the choice between controlled and non-controlled studies significantly influences the study's reliability and accuracy.
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Blind Procedures02:07

Blind Procedures

Ideally, the people who observe and record the children’s behavior are unaware of who was assigned to the experimental or control group, in order to control for experimenter bias. Experimenter bias refers to the possibility that a researcher’s expectations might skew the results of the study. Remember, conducting an experiment requires a lot of planning, and the people involved in the research project have a vested interest in supporting their hypotheses. If the observers knew which child was...
Confounding in Epidemiological Studies01:27

Confounding in Epidemiological Studies

Confounding in statistical epidemiology represents a pivotal challenge, referring to the distortion in the perceived relationship between an exposure and an outcome due to the presence of a third variable, known as a confounder. This variable is associated with both the exposure and the outcome but is not a direct link in their causal chain. Its presence can lead to erroneous interpretations of the exposure's effect, either exaggerating or underestimating the true association. This phenomenon...

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Related Experiment Videos

Reducing unmeasured confounding from non-compliance with randomization in surgical RCTs: a simulation study.

Zhenzhen Lu1,2, Wenwen Li1,2, Mengyao Wang1,2

  • 1Department of Biostatistics, Zhongshan Hospital, Fudan University, Fenglin Road 180, Xuhui District, Shanghai, 200032, China.

BMC Medical Research Methodology
|June 5, 2026
PubMed
Summary
This summary is machine-generated.

Non-compliance in surgical trials causes bias. Double negative controls (DNC) effectively reduce bias and improve accuracy in randomized controlled trials, outperforming traditional methods like intention-to-treat (ITT) and instrumental variable (IV) analysis.

Keywords:
Double negative controlsInstrumental variable analysisNon-complianceRandomized controlled trialsUnmeasured confounding

Related Experiment Videos

Area of Science:

  • Clinical Trials Methodology
  • Biostatistics
  • Surgical Research

Background:

  • Non-compliance with randomization is a significant issue in surgical randomized controlled trials (RCTs).
  • This non-compliance introduces unmeasured confounding, which compromises the validity of causal inference.
  • Traditional methods like intention-to-treat (ITT), per-protocol (PP), as-treated (AT), and instrumental variable (IV) analysis have limitations in addressing this challenge.

Purpose of the Study:

  • To compare the performance of negative control methods (NCM), specifically difference-in-differences (DiD) and double negative controls (DNC), against traditional analytical approaches.
  • To evaluate these methods under realistic conditions informed by lumbar discectomy trials, considering varying crossover rates and confounding structures.

Main Methods:

  • A simulation study was conducted to assess bias, mean squared error (MSE), and coverage probability (CP) of different estimators.
  • Parameters were derived from influential lumbar discectomy trials, simulating crossover rates from 10% to 40%.
  • Evaluated methods included ITT, PP, AT, IV, DiD, and DNC across sample sizes of 100 to 500 and diverse confounding structures.

Main Results:

  • ITT, PP, and AT estimators exhibited severe bias with minimal coverage probability (CP ≤ 0.1%).
  • The IV estimator had low average bias but high variability (MSE = 25.612 at 40% crossover).
  • The DNC estimator demonstrated superior stability and accuracy, with low bias (|bias| ≤ 0.415), low MSE (|MSE| ≤ 2.515), and near-nominal coverage across all tested scenarios. DNC significantly outperformed IV, reducing MSE by over 90% at n=100 and 40% crossover while maintaining high CP (97.7%).

Conclusions:

  • The double negative control (DNC) approach is highly effective in mitigating unmeasured confounding caused by non-compliance in surgical RCTs.
  • DNC offers superior accuracy and reliability compared to conventional methods for causal inference in the presence of non-compliance.
  • This method provides a robust solution for improving the validity of findings from surgical randomized controlled trials.