Interaction effects represent the combined effects of factors on the dependent measure. When an interaction effect is present, the impact of one factor depends on the level of the other factor. For example, imagine a study that tests the effects of a treatment on an outcome measure. The treatment variable is composed of two groups, treatment and control. The results are that the mean for the treatment group is higher than the mean for the control group. But what if the researcher is also interested in whether the treatment is equally effective for females and males. That is, is there a difference in treatment depending on gender group? This is a question of interaction (Stevens, 1999).
I spent a lot of time trying to find an example that I can use to give me a better idea of variables from a work, social, or academic population, and even though I can put forth a definition, I still have a hard time wrapping my head around it. I found this YouTube video on main effects and interaction of sleep deprivation and caffeine that helped a little.
Statistical interaction can be described as the effect of one of the independent variable that may depend on the importance level of another independent variable. For there
to be a statistical interaction there must be a factorial design consisting of two or more independent variables become crossed with each other so that there may be observations at every level of the two or more independents.
In my current position we perform many Mini Mental exams every day to our geriatric inpatient mental health patients. We admit patients with various mental health conditions ranging from depression and being alert and oriented times four, to a stoke or traumatic brain injury who are confused and disoriented. I am going to use the
example of performing research on patients who are alert and oriented times four and staff (if there are not enough participants) in the effects of practice and stress level with the memory task performance using the Mini Mental Exam. The researcher will provide a variety of words to each participant for them to remember and will ask for a recall in a non stressful atmosphere where the participants are told the recall number of words in not important. Later, the researcher will provide the variety of words to be recalled in a
high stressful atmosphere and the researcher stress the importance and expectation of the words to be recalled. The dependent variable in this example should be the words recalled for the list provided by the researcher.