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Related Concept Videos

Group Design02:01

Group Design

The most basic experimental design involves two groups: the experimental group and the control group. The two groups are designed to be the same except for one difference— experimental manipulation. The experimental group gets the experimental manipulation—that is, the treatment or variable being tested—and the control group does not. Since experimental manipulation is the only difference between the experimental and control groups, we can be sure that any differences between the two are due to...
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...
Random Sampling Method01:09

Random Sampling Method

Sampling is a technique to select a portion (or subset) of the larger population and study that portion (the sample) to gain information about the population. Data are the result of sampling from a population. The sampling method ensures that samples are drawn without bias and accurately represent the population. Because measuring the entire population in a study is not practical, researchers use samples to represent the population of interest. Among the various sampling methods used by...
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.
Censoring Survival Data01:09

Censoring Survival Data

Survival analysis is a statistical method used to analyze time-to-event data, often employed in fields such as medicine, engineering, and social sciences. One of the key challenges in survival analysis is dealing with incomplete data, a phenomenon known as "censoring." Censoring occurs when the event of interest (such as death, relapse, or system failure) has not occurred for some individuals by the end of the study period or is otherwise unobservable, and it might have many different reasons...

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Related Experiment Video

Updated: Jul 6, 2026

Comparing the Frequency Effect Between the Lexical Decision and Naming Tasks in Chinese
08:08

Comparing the Frequency Effect Between the Lexical Decision and Naming Tasks in Chinese

Published on: April 1, 2016

Allocation concealment in randomised trials: defending against deciphering.

Kenneth F Schulz1, David A Grimes

  • 1Family Health International, PO Box 13950, 27709, Research Triangle Park, NC, USA. KSchulz@fhi.org

Lancet (London, England)
|February 28, 2002
PubMed
Summary
This summary is machine-generated.

Proper allocation concealment is essential for unbiased randomized controlled trials. Without it, trial results can be skewed, emphasizing the need for clever trial design to prevent manipulation.

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Area of Science:

  • Clinical Trials Methodology
  • Biostatistics
  • Research Integrity

Background:

  • Randomized controlled trials (RCTs) are fundamental to evidence-based medicine.
  • Adequate allocation concealment is critical for maintaining the integrity of RCTs.
  • Subversion of random allocation sequences can occur if concealment is inadequate.

Purpose of the Study:

  • To highlight the importance of robust allocation concealment in RCTs.
  • To discuss the challenges and implications of inadequate allocation concealment.
  • To emphasize the need for clever trial design to prevent bias.

Main Methods:

  • The abstract discusses the principles of allocation concealment in clinical trial design.
  • It examines the potential for subversion of random allocation sequences.
  • It reviews the impact of inadequate concealment on treatment effect estimates.

Main Results:

  • Inadequate allocation concealment leads to biased estimates of treatment effect, often exaggerated.
  • Tampering with allocation undermines the validity and reliability of trial findings.
  • Clever design strategies are necessary to prevent investigators from deciphering allocation sequences.

Conclusions:

  • Effective allocation concealment is paramount to immunize trials against selection and confounding biases.
  • Trial designers must be vigilant and employ sophisticated methods to ensure concealment.
  • Reporting baseline comparisons is important, but hypothesis testing on these is discouraged.