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Related Concept Videos

Randomized Experiments01:13

Randomized Experiments

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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
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Naturalistic Observations02:30

Naturalistic Observations

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If you want to understand how behavior occurs, one of the best ways to gain information is to simply observe the behavior in its natural context. However, people might change their behavior in unexpected ways if they know they are being observed. How do researchers obtain accurate information when people tend to hide their natural behavior? As an example, imagine that your professor asks everyone in your class to raise their hand if they always wash their hands after using the restroom. Chances...
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Bystander Effect02:09

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The discussion of bullying highlights the problem of witnesses not intervening to help a victim. This is a common occurrence, as the following well-publicized event demonstrates. In 1964, in Queens, New York, a 19-year-old woman named Kitty Genovese was attacked by a person with a knife near the back entrance to her apartment building and again in the hallway inside her apartment building. When the attack occurred, she screamed for help numerous times and eventually died from her stab wounds.
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Regression Toward the Mean01:52

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Regression toward the mean (“RTM”) is a phenomenon in which extremely high or low values—for example, and individual’s blood pressure at a particular moment—appear closer to a group’s average upon remeasuring. Although this statistical peculiarity is the result of random error and chance, it has been problematic across various medical, scientific, financial and psychological applications. In particular, RTM, if not taken into account, can interfere when...
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Group Design02:01

Group Design

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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...
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Blinding01:11

Blinding

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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.
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Related Experiment Video

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Combining Behavioral Endocrinology and Experimental Economics: Testosterone and Social Decision Making
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Neighborhood effects in a behavioral randomized controlled trial.

Sandi L Pruitt1, Tammy Leonard2, James Murdoch3

  • 1Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA; Harold C. Simmons Comprehensive Cancer Center, 5323 Harry Hines Blvd, Dallas, TX 75390-9169, USA.

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Summary

Neighborhood effects significantly impacted a colorectal cancer (CRC) screening trial. Social interactions between participants can contaminate intervention arms and bias results in health behavior randomized controlled trials (RCTs).

Keywords:
Cancer screeningNeighborhoodPeer relationshipsRandomized controlled trialSpatial autocorrelation

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Area of Science:

  • Public Health
  • Epidemiology
  • Biostatistics

Background:

  • Randomized controlled trials (RCTs) evaluating health behavior interventions may be confounded by unmeasured neighborhood effects.
  • Social interactions among participants can lead to intervention arm contamination and biased effect size estimation.
  • Previous RCTs have not adequately considered spatially-varying covariates like neighborhood influences.

Purpose of the Study:

  • To investigate the presence and impact of neighborhood effects in a randomized controlled trial (RCT) for colorectal cancer (CRC) screening.
  • To determine if social interactions among participants influence individual screening behavior.
  • To highlight the need for considering neighborhood effects in future health behavior intervention RCTs.

Main Methods:

  • Analysis of a large-scale RCT (N=5628) designed to increase CRC screening uptake.
  • Statistical examination of the association between average CRC test use among neighbors and individual CRC test use.
  • Assessment of potential intervention arm contamination due to spatially-varying covariates.

Main Results:

  • Statistically significant neighborhood effects were identified in the CRC screening RCT.
  • Higher CRC test use among neighbors was positively associated with individual participants' CRC test use.
  • Evidence suggests that social interactions can influence health behavior outcomes in RCT settings.

Conclusions:

  • Neighborhood effects represent a significant, previously unaddressed, factor in health behavior RCTs.
  • Future RCTs should incorporate assessments of social interactions to mitigate potential bias.
  • Accounting for neighborhood effects is crucial for accurate intervention effect estimation in public health research.