I’m studying for my Statistics class and don’t understand how to answer this. Can you help me study?

It is interesting how much preparation goes into a study and the level of scrutiny the study undergoes in order to prove its reliability, validity and relevance. In evidence-based practice, the term ‘evidence’ is used instead of proof, which emphasizes that evidence is not the same as proof and that evidence can be so weak that it is hardly convincing or can be so strong that no one doubts its correctness. It is, therefore, essential for one to determine which evidence is the most suitable and using that evidence to make clinical decisions. ‘levels of evidence’ are used for this purpose and specify a hierarchical order for various research designs based on their internal validity.