The corresponding question to SN vs. performance is related to how you guarantee the quality of time and how students utilize their time on SN... Other than their self reported surveys
dr i think there are more than one variable affect on the quality of time spent on social media. such as the purpose of using social media, -as a part of reasons for using internet in general- the quality can be measured maybe as relativity, purpose of using according to the time spent on using social media.
Time and purpose may be considered as independent variable, and other variables such demographic as dependent variables.
Also I think purpose for using may be analyzed through
aggregation or clustering.
I think we can develop a model...
This question rich strong and attractive for doing a research,,,
I guess we can measure time also by designing objectives measures of time production.... What is your business (even if you are a student), how far can a student benefit from social media...