What research shows how assessment design can minimize plagiarism? This past semester has seen an unusually high number of students plagiarizing in one of the subjects I teach. To be specific, it was five times the previous maximum I had seen. This has lead me down the path of digging into ways to reduce plagiarism from my students.

I read this question which was great and had several good answers but it was broadly focused. I would like to dig a bit deeper into one specific area: How can assessment design be used to minimize plagiarism?

I realize that exams are less likely to have plagiarism but I want to avoid those because they are timed and I don't want my students to be assessed in non-real-world situations like that. So, I want the assessments to be take-home but I don't want to put more constraints on this question.

I really want to know what research has been done showing the effect of different assessment design and how it has impacted student-plagiarism (with a focus on what minimizes plagiarism)?
According to your profile, you teach management. So we are looking at writing, rather than equations?  

This review article discusses steps taken at a university in Australia, and provides some lit review. It is open-source. In regards to research on assessment design, it recommends:


Regularly change the questions/prompts 
Projects should require original analysis rather than be summaries or definitions.
More marks should be associated with the process of project creation, rather than the final draft. Examples of intermediate assignments are research journals, annotated bibliographies, and first drafts.
Change product from text-only to something else - a poster, an oral presentation.


Above is the "answer" to your question. You may also want to consider why your plagiarism is suddenly increasing. The linked article points out that many students plagiarize because of lack of training in how to effectively write without copying a source. If you have a cohort of students from a background of poorer preparation, I would recommend a module on how to write without plagiarism. 

Best of luck.