Which of these designs does the best job of controlling extraneous subject variables?
Extraneous VariableBy Dr. Saul McLeod, updated 2019 Show
When we conduct experiments there are other variables that can affect our results, if we do not control them.
The researcher wants to make sure that it is the manipulation of the independent variable that has an effect on the dependent variable. Hence, all the other variables that could affect the dependent variable to change must be controlled. These other variables are called extraneous or confounding variables. Extraneous variables should be controlled were possible, as they might be important enough to provide alternative explanations for the effects. There are four types of extraneous variables:1. Situational VariablesThese are aspects of the environment that might affect the participant’s behavior, e.g. noise, temperature, lighting conditions, etc. Situational variables should be controlled so they are the same for all participants. Standardized procedures are used to ensure that conditions are the same for all participants. This includes the use of standardized instructions 2. Participant / Person VariableThis refers to the ways in which each participant varies from the other, and how this could affect the results e.g. mood, intelligence, anxiety, nerves, concentration etc. For example, if a participant that has performed a memory test was tired, dyslexic or had poor eyesight, this could effect their performance and the results of the experiment. The experimental design chosen can have an affect on participant variables. Situational variables also include order effects that can be controlled using counterbalancing, such as giving half the participants condition 'A' first, while the other half get condition 'B' first. This prevents improvement due to practice, or poorer performance due to boredom. Participant variables can be controlled using random allocation to the conditions of the independent variable. 3. Experimenter / Investigator EffectsThe experimenter unconsciously conveys to participants how they should behave - this is called experimenter bias. The experiment might do this by giving unintentional clues to the participants about what the experiment is about and how they expect them to behave. This affects the participants’ behavior. The experimenter is often totally unaware of the influence which s/he is exerting and the cues may be very subtle but they may have an influence nevertheless. Also, the personal attributes (e.g. age, gender, accent, manner etc.) of the experiment can affect the behavior of the participants. 4. Demand CharacteristicsDemand characteristics are all the clues in an experiment which convey to the participant the purpose of the research. Demand characteristics can change the results of an experiment if participants change their behavior to conform to expectations. Participants will be affected by: (i) their surroundings; (ii) the researcher’s characteristics; (iii) the researcher’s behavior (e.g. non-verbal communication), and (iv) their interpretation of what is going on in the situation. Experimenters should attempt to minimize these factors by keeping the environment as natural as possible, carefully following standardized procedures. Finally, perhaps different experimenters should be used to see if they obtain similar results. Suppose we wanted to measure the effects of Alcohol (IV) on driving ability (DV) we would have to try to ensure that extraneous variables did not affect the results. These variables could include:
If these extraneous variables are not controlled they may become confounding variables, because
they could go on to affect the results of the experiment. How to reference this article:How to reference this article:McLeod, S. A. (2019, July 30). Extraneous variable. Simply Psychology. www.simplypsychology.org/extraneous-variable.html Home | About Us | Privacy Policy | Advertise | Contact Us Simply Psychology's content is for informational and educational purposes only. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment. © Simply Scholar Ltd - All rights reserved Which design within or between subjects controls extraneous variables better?Within-subjects experiments have the advantage of controlling extraneous participant variables, which generally reduces noise in the data and makes it easier to detect a relationship between the independent and dependent variables.
Which of the following is a way of controlling extraneous variables?Randomization is the preferred method for controlling extraneous variables.
Why is it important to control extraneous variables to the best extent possible )?Extraneous variables can threaten the internal validity of your study by providing alternative explanations for your results. In an experiment, you manipulate an independent variable to study its effects on a dependent variable.
Which study design allows researchers to control variables?Experimental research allows the researcher to control the situation. In so doing, it allows researchers to answer the question, “what causes something to occur?” Permits the researcher to identify cause and effect relationships between variables and to distinguish placebo effects from treatment effects.
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