Extraneous variables may have an influence on the dependent variable. In what ways do researchers attempt to control extraneous variables?
Extraneous variables are variables which have not been controlled while dependent variables are the probability of achieving success. Extraneous variables have influence to the outcome and researchers use some methodology to control them.One of the ways researchers use is making the extraneous variable constant where they try to ensure that there are no changes in the values taken by the extraneous variables during experiments through randomization. For example, when one is testing the effect of temperature on plant growth soil type and amount of water to be constant. These are extraneous variables that affect the experiment. This method of randomization can be considered equivalent in all ways when experiment begins, and it is the possible method to avoid extraneous variables.
The method of matching is also used. Experimenter chooses subjects who match each other. Researchers make sure that the species they use in experiments are of the same type, age and weight. For example, a researcher decides to experiment the effect of growers mash to growers. He should choose a chick of the same initial weight, type and age because this will be the extraneous variables.The homogeneous sample is also a way of dealing with these variables, and it is a simple and effective way of controlling extraneous variable. For example, study of pain, one should take different culture group, and this will eliminate the variables that may state the response of pain to different cultures.
Some can also be controlled by designing them out of the experiment. For instance, differences between people in an experiment can be eliminated through assigning different people in different groups according to the differences during the sampling process.
Building extraneous variables into the experiment is also a way of dealing of the outcome. When extraneous variables cannot be dealt with by the randomization method, then they can be included into the design. The effect of these variables can be measured and separated from the outcome u wanted to get initially.
Reference
Waltz, C. F., Strickland, O., & Lenz, E. R. (2005). Measurement in nursing and health research (3rd ed.). New York: Springer Pub.
