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Between Subjects Design
Martyn Shuttleworth 257.3K reads
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A between subjects design is a way of avoiding the carryover effects that can plague within subjects designs, and they are one of the most common experiment types in some scientific disciplines, especially psychology.
The basic idea behind this type of study is that participants can be part of the treatment group or the control group, but cannot be part of both. If more than one treatment is tested, a completely new group is required for each.
What is a Between Subjects Design?
A group of researchers wants to test some modifications to the educational program and decide upon three different modifications.
They pick a school and decide to use the four existing classes within an age group, assuming that the spread of abilities is similar. Each group of children is given a different educational program, along with a control group sticking with the original. All of the groups are tested, at the end, to determine which program delivered the most improvement.
If the researchers want to be a little more accurate and reduce the chances of differences between the groups having an effect, they use modifications of the design.
For example, maybe one class had a great teacher and has always been much more motivated than the others, a factor that would undermine the validity of the experiment. To avoid this, randomization and matched pairs are often used to smooth out the differences between the groups.
Between Subjects Design
Advantages of Between Subjects Design
Between subjects designs are invaluable in certain situations, and give researchers the opportunity to conduct an experiment with very little contamination by extraneous factors.
This type of design is often called an independent measures design because every participant is only subjected to a single treatment. This lowers the chances of participants suffering boredom after a long series of tests or, alternatively, becoming more accomplished through practice and experience, skewing the results.