A key component of experimental design involves making decisions about the manipulation of the treatment conditions. In this post, we will look at the following traits of treatment conditions
- Treatment Variables
- Experimental treatment
Lastly, we will examine group comparison.
One of the most common independent variables in experimental design are treatment and measured variables. Treatment variables are manipulated by the researcher. For example, if you are looking at how sleep affects academic performance, you may manipulate the amount of sleep participants receive in order to determine the relationship between academic performance and sleep.
Measured variables are variables that are measured by are not manipulated by the researcher. Examples include age, gender, height, weight, etc.
An experimental treatment is the intervention of the researcher to alter the conditions of an experiment. This is done by keeping all other factors constant and only manipulating the experimental treatment, it allows for the potential establishment of a cause-effect relationship. In other words, the experimental treatment is a term for the use of a treatment variable.
Treatment variables usually have different conditions or levels in them. For example, if I am looking at sleep’s affect on academic performance. I may manipulate the treatment variable by creating several categories of the amount of sleep. Such as high, medium, and low amounts of sleep.
Intervention is a term that means the actual application of the treatment variables. In other words, I broke my sample into several groups and caused one group to get plenty of sleep the second group to lack a little bit of sleep and the last group got nothing. Experimental treatment and intervention mean the same thing.
The outcome measure is the experience of measuring the outcome variable. In our example, the outcome variable is academic performance.
Experimental design often focuses on comparing groups. Groups can be compared between groups and within groups. Returning to the example of sleep and academic performance, a between group comparison would be to compare the different groups based on the amount of sleep they received. A within group comparison would be to compare the participants who received the same amount of sleep.
Often there are at least three groups in an experimental study, which are the controlled, comparison, and experimental group. The controlled group receives no intervention or treatment variable. This group often serves as a baseline for comparing the other groups.
The comparison group is exposed to everything but the actual treatment of the study. They are highly similar to the experimental group with the experience of the treatment. Lastly, the experimental group experiences the treatment of the study.
Experiments involve treatment conditions and groups. As such, researchers need to understand their options for treatment conditions as well as what types of groups they should include in a study.