Question

While within-subjects designs often require fewer subjects, that in itself can lead to issues in terms of the data. For instance, subjects are being used in multiple trials, so they would typically be more tired of the study, especially if it's the same general experiment performed repeatedly over consecutive trials. This can lead to multiple confounds, such as the subject not participating as they normally would, or even dropping out of the study and therefore nullifying any of the data previously collected. Regardless of what happens, it can interfere with the interpretation of the results. It therefore seems that while it uses fewer subjects, the risk is that you may need to run a study again if you have enough subjects drop out. For instance, imagine you had a within-subjects design that only required 12 subjects. If half of them drop out, that may not be enough to run a complete analysis, so you may need to run another study. In the end, running repeated trials will cost more than running one larger trial. In this respect, do you think within-subjects designs pose more of an issue than the benefits they seem to provide?

Answer 1

A within-subject design is a type of design in which all participants are exposed to every condition.This design is also called as a Repeated measures design. In a within-subjects design, there is only one group and each one of the participants will participate in all level of the independent variable. The goal of this design is to see whether one treatment is better than the other.

One of the most important  benefits of this type of design is that it does not require a large pool of participants.It also help to reduce errors associated with individual differences.Here, the individuals are exposed to all medium of a treatment, so individual differences will not distort the results.

A major drawback of using a within-subject design is Fatigue. Participants may become bored or uninterested by taking part in multiple treatments. Another draw back is that it may be time consuming. One of the other limitation in within-subject design is carry-over effect. Carry-over effect can cause the data to be invalid and it may  due to the experience of one conditions that may effect the results of another condition.

There are benefits and issues in all type of experimental design. As within-subject design has its own advantages and disadvantages, it is more preferred in scientific experiment group design.