Design is the next factor to consider when you’re writing your question. Design is a little different from the other aspects of PICO because you don’t usually include this information in your actual question, but it’s a crucial part of your research strategy. You’ll usually see the design portion of PICO (D) described in a systematic review’s inclusion and exclusion criteria.
Basically, you need to specify the design, or the types of studies, you want to include in your systematic review. These studies will form the “ingredients” for your systematic review.
We’ll talk more about how to pick those ingredients on the next few pages.