Replication of an existing study may be possible in certain circumstance. Each school has established guidelines on what methodologies may be used in the dissertation. Additionally, some schools have placed limits on replication of existing studies, particularly studies done as dissertations by others.  You will need to consult with your school's guidelines for further information under your school on the PhD page on IGuide.

If you are able to replicate a study for your dissertation, remember that you are required to get permission to use the instrument from the original creator of the dissertation. You must also obtain permission to use any modified instruments if those were employed in the study. It is a violation of copyright law to use an instrument without permission.

Additionally, you must give due credit in the dissertation to the study you are replicating. It must be clear within chapters 3, 4, and 5 that you are replicating an existing study. You must further take care to ensure that if your study draws the same conclusion or similar conclusions that these are discussed appropriately within the dissertation with appropriate discussion of the original study. When replicating a study, it is easy to potentially plagiarize, therefore you must be certain the original study is cited appropriate.