Experimental design

Variables

The two major variables in an experiment are dependent and independent variable. An independent variable is considered as a variable that stands alone and is not influenced by other variables being measured (McLeod, 2008).Therefore, the independent variable is one that the experimenter changes and is presumed to have a straight influence on the dependent variable. For instance, participants can be allocated to a drug to be measured any changes in their level of anxiety. Thus, the dependent variable is being measured and tested in the study and is dependent on the independent variable.

Ideally, the independent variable is controlled and changed in a scientific study to examine the effects of the dependent variable. While the researcher alters the independent variable, the influence of the dependent variable is being recorded and observed. The independent variable differs amid groups being compared which means that individuals of the same group will have a similar variable but members of the second group will have a different level of independent variable (McLeod, 2008).

The extraneous variables are considered as all variables that are not independent variables but can influence the findings of the study (McLeod, 2008). Therefore, the extraneous variables that could influence the dependent variable must be controlled. This is because they have a possibility of offering an alternative explanation for the influences. An example could be system’s workload which may influence some of the quality attributes such as the response time. The extraneous variable leads to an association between the two variables that not casually linked.

The extraneous variables are a challenge to the external and internal validity of an experiment since they affect the dependent variable and influence the outcome of a research study (Rosenberg, 2017). Researchers rely on various ways to control the effects of the extraneous variable. Randomization and experimental designs have been used to control extraneous variables. In randomization, the treatments are assigned randomly to the experimental groups. For instance, an experiment can involve large sample size with different age, gender and income. The experimental design plays a great role in lowering the impact and role of the extraneous variable.

 

 

References

McLeod, S. A. (2008). Independent, dependent and extraneous variables. Simply Psychology.

Rosenberg, M. (2017). Extraneous variables. Research Design: The Logic of Social Inquiry, 263.