Controlling extraneous variables

Comment #1

Extraneous variables in research can have affect the different  variable in a study.  “Controlling extraneous variables  enables researchers to determine the effects of an intervention or  treatment on study outcomes more accurately”(Grove, Gray &  Burns, 2015).  Researchers can control the extraneous variables  by manipulating the environment, subjects, settings and treatment  interventions. Extraneous variables are more involved in  Quasi-Experimental type studies.  These types of studies have to  do with effectiveness of treatment in a partially controlled  environment.  There are 4 different types of extraneous variables  which are demand characteristics, experimenter effects, Participant  variable and situational variables.  One way researchers can  control extraneous variables is through random sampling.  When  random sampling is done, it does not completely eliminate extraneous  variable, it only ensure quality between all groups.  If random  sampling is not used, the effect the extraneous variable may have on  the study results be a lot more of a concern at the end of the study  being conducted (Stephanie, 2015).


Grove, S. K., Gray, J., & Burns, N. (2015). Understanding  nursing research: Building an evidence-based practice. St. Louis, MO: Elsevier.

Stephanie. (2015, May 10). Extraneous Variable Simple Definition.  Retrieved from


In order to understand research related to healthcare it is important  to understand the terminology. The term variable is used frequently  when referring to research. “The simplest definition of a  variable is that it is something that takes on different values”   (Flannelly, Flannelly, & Jankowski, 2014). Extraneous variables  are “variables that exist in all studies and can affect the  measurement of study variables and the relationships among these  variables” (Grove, Gray, & Burns, 2015). Often in healthcare  research the term treatment or intervention are used to describe an  independent variable. Outcome is used to describe the dependent  variable. “Researchers are concerned about extraneous variables  because they can alter or obscure the relationship between the  independent variable and the dependent variable, or indicate there is  a causal relationship between them when none exists” (Flannelly  et al., 2014). One way is to try to control the confounds of the  subject such as age and gender. “Another way is to incorporate  an extraneous variable as an independent variable in the study  design” (Flannelly et al., 2014). Flannelly et al. give the  example of grouping participants into age groups. “The third way  is to use the person’s age as an independent variable in the  statistical analysis” (Flannelly et al., 2014).


Flannelly, L., Flannelly, K., & Jankowski, K. (2014).  Independent, dependent, and other variables in healthcare and  chaplaincy research. Journal of Health Care Chaplaincy,  20,
161-170. doi:10.1080/08854726.2014.959374

Grove, S., Gray, J., & Burns, N. (2015). Understanding nursing  research: Building an evidence-based practice. (6th ed.)  St. Louis, MO: Saunders.

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