https://creativecommons.org/licenses/by-nc-sa/4.0/ Brad Long
This is what is known as the Evidence Based Pyramid. The higher you go in the pyramid, the stronger the evidence. So Systematic Reviews/Meta Analysis are at the top. Your question will determine what type of study you are looking for. This chart shows for each type of question, the highest level of evidence/type of study you are looking for.
Used with permission from Duke Medical School -https://guides.mclibrary.duke.edu/ebm/pico