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Ethics & Safety Intermediate 2 min read

What is experimenter's bias?

A type of bias that occurs when an experimenter's expectations or beliefs influence the outcome of an experiment

Experimenter's bias happens when the person conducting an experiment unintentionally affects the results because of their own preconceived notions or expectations. This can be due to various factors, such as how they interact with participants, interpret data, or make decisions during the experiment.

Experimenter's bias is like a referee in a sports game who, without realizing it, is making calls that favor one team over the other because they are a fan of that team. Just as the referee's bias can influence the outcome of the game, an experimenter's bias can influence the outcome of an experiment.

A researcher studying the effects of a new drug might, without realizing it, give more attention or encouragement to participants who are receiving the drug, which could lead to better outcomes for those participants and skew the results of the study.

Experimenter's bias can be used to describe situations where researchers, often unintentionally, influence their experiments in ways that affect the results, such as through their body language, the way they ask questions, or how they handle and interpret data.

One common misconception is that experimenter's bias only occurs when researchers intentionally try to manipulate results. However, it can also occur unintentionally, simply because of the researcher's expectations or beliefs.

The concept of experimenter's bias has been recognized for many decades and is a significant concern in fields such as psychology, medicine, and social sciences, where the influence of the experimenter can significantly impact the validity of research findings.

observer bias researcher bias expectation bias

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