In research, an experimenter bias, also known as research bias, occurs when a researcher unconsciously affects results, data, or a participant in an experiment due to subjective influence. It is difficult for humans to be entirely objective which is not being influenced by personal emotions, desires, or biases.
Experimenter bias can occur at any phase of the research process from the initial background research to the final write-up of results. It is very important to consider experimenter bias as a possible issue in any research setting. Steps can be taken to reduce the likelihood of its occurrence such as conducting blind studies and finding non-biased data collectors.