What phenomenon occurs when a researcher's bias influences the outcome of a study?

The phenomenon that occurs when a researcher's bias influences the outcome of a study is known as experimenter bias. This type of bias can manifest in various ways, such as in the way the researcher conducts the study, interacts with participants, or interprets the data. For instance, if a researcher has a preconceived notion about what the study should reveal, they might inadvertently alter how they collect data or respond to participants, leading to results that favor their hypothesis rather than an objective assessment of the data.

Experimenter bias undermines the validity of the research findings because it introduces a subjectivity that skews the results. To mitigate this bias, researchers often employ methods such as double-blind studies, where neither the participants nor the experimenters know who is receiving a particular treatment, to ensure that personal beliefs do not affect the study's outcomes. This highlights the importance of maintaining objectivity and employing rigorous methodologies in scientific research to achieve reliable and valid results.