Within-Subject Independent Variable
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A Within-Subject Independent Variable is an independent variable that is manipulated by testing each subject at each level of the variable.
- AKA: Within-Subjects Factor, Within-Subjects Variable, Repeated-Measures Factor, Repeated-Measures Variable.
- See: Between-Subject Independent Variable.
References
2012
- http://onlinestatbook.com/2/glossary/within-subjects.html
- A within-subjects variable is an independent variable that is manipulated by testing each subject at each level of the variable. Compare with a between-subjects variable in which different groups of subjects are used for each level of the variable.
- http://davidmlane.com/hyperstat/A135184.html
- A within-subjects variable is an independent variable that is manipulated by testing each subject at each level of the variable. Consider an experiment examining the effect of study time on memory. Subjects are given a list of 10 words to study for later recall. In one condition, subjects are given one minute to study the list; in the other condition, subjects are given two minutes. Each subject is tested once in each condition. Therefore, subjects have two scores, one for the one-minute condition and one for the two-minute condition.(Naturally, subjects are given different lists of words each time. Half of the subjects are tested with the one-minute condition first; the other half are tested with the two-minute condition first). The variable "study time" is a within-subjects variable since each subject is tested under each of the two levels of the variable (one minute and two minutes). The same subjects are used in both conditions so the comparison between conditions can be made within each of the subjects.
- http://onlinestatbook.com/2/research_design/designs.html
- A within-subjects design differs from a between-subjects design in that the same subjects perform at all levels of the independent variable. For example consider the "ADHD Treatment" case study. In this experiment, subjects diagnosed as having attention deficit disorder were each tested on a delay of gratification task after receiving methylphenidate (MPH). All subjects were tested four times, once after receiving one of the four doses. Since each subject was tested under each of the four levels of the independent variable "dose," the design is a within-subjects design and dose is a within-subjects variable. Within-subjects designs are sometimes called repeated-measures designs.