According to Grove, Gray, & Burns (2015), extraneous variables are present in all studies and can affect the study and the relationships among the variables. Researchers
must continually look for extraneous variables throughout the research to prevent a biased impact. They can be confounding, which means they are not recognized until the study is in progress, or environmental, which includes the climate, family, etc. Extraneous variables are more of a concern in quantitative research because they can prevent the researcher from obtaining a clear understanding and they are not recognized until the study is in progress but profoundly affect the outcome of the study (Gray, et al, 2015). While in most qualitative studies, extraneous variables are usually controlled because subjects are studied in their natural environments. By selecting a sampling of
participants who are characteristic of the population being studied, extraneous variables can be controlled by the researcher. Grove, et al (2015) provides the example of research on the effect of relaxation therapy and the patient’s perception of incisional pain. In order to control extraneous variables, the researcher needed a sampling of patients who are in a hospital environment and receiving one type of intravenous pain medication. This type of sampling would reduce the extraneous variables such as surgical incision and time, amount and type of pain medication administered postoperatively and their perception of incisional pain (Grove, et al, 2015).
There are 4 types of extraneous variables:
*Situational variables- which are aspects of the environment that might affect the participant’s behavior. For example; noise, temperature, lighting conditions. Situational variables should be controlled so they are the same for all participants.
*Participant/person variables- This refers to the ways in which each participant varies from the other, and how this could affect the results. For example; mood, intelligence, anxiety, nerves, concentration.
*Experimenter/ investigator effects- The experimenter unconsciously conveys to participants how they should behave – this is called experimenter bias.
*Demand characteristics- these are all the clues in an experiment which convey to the participant the purpose of the research. Experimenters should attempt to minimize these factors by keeping the environment as natural as possible, carefully following standardized procedures.