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Related Concept Videos

Positive and Negative Feedback Loops01:18

Positive and Negative Feedback Loops

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:
Attitudes01:54

Attitudes

Attitude is our evaluation of a person, an idea, or an object. We have attitudes for many things ranging from products that we might pick up in the supermarket to people around the world to political policies. Typically, attitudes are favorable or unfavorable: positive or negative (Eagly & Chaiken, 1993). And, they have three components: an affective component (feelings), a behavioral component (the effect of the attitude on behavior), and a cognitive component (belief and knowledge;...
Positive, Negative, and Zero Work00:58

Positive, Negative, and Zero Work

Work is done on an object when energy is transferred to the object. In other words, work is done when a force acts on a body that undergoes a displacement from one position to another. By definition, the work done by a force is the integral of the force with respect to the displacement along its path. Forces can vary as a function of position, and displacements can occur along various paths between two points. The magnitude of a force multiplied by the cosine of the angle that the force makes...
Social Facilitation01:04

Social Facilitation

Not all intergroup interactions lead to negative outcomes. Sometimes, being in a group situation can improve performance. Social facilitation occurs when an individual performs better when an audience is watching than when the individual performs the behavior alone. This typically occurs when people are performing a task for which they are skilled.
Self-Evaluation: Self-Enhancement and Self-Verification03:00

Self-Evaluation: Self-Enhancement and Self-Verification

Social psychologists have documented that feeling good about ourselves and maintaining positive self-esteem is a powerful motivator of human behavior (Tavris & Aronson, 2008). In the United States, members of the predominant culture typically think very highly of themselves and view themselves as good people who are above average on many desirable traits (Ehrlinger, Gilovich, & Ross, 2005). Often, our behavior, attitudes, and beliefs are affected when we experience a threat to our...
Negative and Positive Feedback01:18

Negative and Positive Feedback

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:

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Related Experiment Video

Updated: Jun 16, 2026

Tickling, a Technique for Inducing Positive Affect When Handling Rats
05:37

Tickling, a Technique for Inducing Positive Affect When Handling Rats

Published on: May 8, 2018

Invited commentary: positivity in practice.

Daniel Westreich1, Stephen R Cole

  • 1Department of Epidemiology, University of North Carolina, Chapel Hill, NC 27599-7435, USA. djw@unc.edu

American Journal of Epidemiology
|February 9, 2010
PubMed
Summary
This summary is machine-generated.

Positivity, an essential assumption for causal inference in epidemiology, ensures data exists for all confounder combinations. This study defines positivity and offers practical methods for examining and addressing its violations in research.

Related Experiment Videos

Last Updated: Jun 16, 2026

Tickling, a Technique for Inducing Positive Affect When Handling Rats
05:37

Tickling, a Technique for Inducing Positive Affect When Handling Rats

Published on: May 8, 2018

Area of Science:

  • Epidemiology
  • Causal Inference
  • Statistical Modeling

Background:

  • Positivity, or the experimental treatment assignment assumption, is crucial for valid causal inference in observational studies.
  • This assumption requires the presence of both exposed and unexposed individuals across all combinations of observed confounder values.
  • Positivity is frequently overlooked in epidemiological practice, potentially compromising study validity.

Purpose of the Study:

  • To define and clarify the concept of positivity in epidemiological research.
  • To distinguish between deterministic and random positivity.
  • To provide practical guidance for assessing and addressing positivity violations in data analysis.

Main Methods:

  • Conceptual definition and elaboration of the positivity assumption.
  • Distinction between deterministic and random positivity.
  • Illustrative examples using 2x2 tables.
  • Discussion of methods for empirical examination of positivity.

Main Results:

  • Positivity is a fundamental requirement for drawing causal conclusions from observational data.
  • Nonpositivity can arise from deterministic or random factors, impacting inference.
  • Methods exist to identify and manage violations of the positivity assumption.

Conclusions:

  • Epidemiologists must actively assess and address positivity to ensure the reliability of causal effect estimates.
  • Understanding and applying positivity principles enhances the rigor of observational studies.
  • The presented framework aids researchers in navigating and overcoming challenges related to positivity in practice.