When designing experiments, researchers always find themselves needing to control certain variables to ensure the success of the research. According to Sytsma (2009), a variable is defined as almost anything found on the face of the earth. Variables are a real concern for researchers (Sytsma, 2009). When these variables are of definite experimental interests they are known as factors. However, the term factor is generally used when an experiment includes more than just one variable (Sytsma, 2009).
Variables that Researchers can Control
Among the variables that a researcher can control while designing the experiment are history, maturation and pre-testing (Key, 1997). The environment of the experiment and the actual variable to be used in the experiment may also be controlled by the researcher (Student of Fortune, 2011).
As a factor, history can easily affect the results of a study when a researcher takes further measurements to the experimental variables that had not been taken earlier before the onset of the research. An example, consider a case where a researcher collects data before and after a certain event happens. If not properly controlled, this may greatly affect the results of a study as measurements or data collected could greatly differ (Key, 2009).
Maturation refers to the process of an individual moving on to maturity either in age or otherwise during the life period of the research. The data collected at different stages of the research may be affected by change in time and hence the need for effective controls (Key, 2009).
Pre-testing on the other hand requires that the researcher notes down some parameters before the actual research begins. The challenge faced by the researcher has to do with the fact that experimental conditions could change drastically in the process in such a way that the results of any post-test may end up be being skewed (Key, 2009). It is very typical for respondents to give completely different responses at a later stage of the research leading to invalid results (Key, 2009).
Limit the Effects of Extraneous Variables
According to Sytsma (2009), when variables are external with regard to the experiment, they are referred to as being extraneous. Without proper control, these variables end up influencing or affecting the results of the research.
To limit the effect of extraneous variables, a researcher may need to control the degree of randomness of the experimental variable (Student of Fortune, 2011). Randomization commonly refers to the fact that the outcome of a research is not at all predictable. A researcher’s confidence has been known to come from understanding that a random approach was taken at the time of assigning experimental variables (Sytsma, 2009).
Extraneous variables can also be dealt with by means of Control Groups. This involves the use of a matched group that is not exposed to the experimental variables. The control groups can help greatly in reducing the effect of factors such as history and maturation. Generally, the control group is subjected to every other experimental condition but not to the experimental variable (Key, 1997).
Another approach to addressing the effect of extraneous variables is to use additional groups. These are groups that were neither tested in advance nor exposed to the experimental preparations and can thus be used in tackle the effects of pre-tests (Key, 1997). They are used together with the pre-tested groups or other factors that affect the results of a study.