Knowing when to use the correct tense can be tricky. In generally, you use:
The past simple for past events or actions that are completed and have no connection to the here and now.
The present perfect for actions which started in the past and are still happening now OR for finished actions which have a connection to the present.
Here are some tips that might help
When you are writing your paper, ask yourself the following questions?
1) Does this refer to a specific study or a specific action in the past? If so, use the past tense. For example:
In 2008, Yorkville University conducted a study on student retention. (Specific study noted on a specific date)
2) Are you referring to general actions? If so, use the perfect tense. For example:
Psychologists have been conducting studies based on personality traits. (The perfect tense works here because you are not referring to anything specific. If the next sentence was to reference a specific study, you would switch to the past tense.)
3) Is this something that started in the past and is still occurring today? If so, use the perfect tense. For example:
Yorkville University has been conducting studies on student retention since 2008. (This shows an action that started in the past but is still happening today. It is not a completed action)