If I want to sent a weekly survey to employees and track the trends week over week or month over month, what is the best way to go about this? Should I copy the same survey or send the same original survey to a different contact list?

In a typical scenario, you would send the same survey to a new mailing list.

Hello @ER2018 , You can add filter in Data & Analysis -> Data option as shown in the image below!Next select your required operator!