At the uni we did a research in our group and used a correlational test to investigate the relationships... however our degrees of freedom equaled to the sample size (df = n) and when the tutor was asked why it isn't n - 2 she said it was because we were not interested in the population, but she couldn't explain it further.

Could someone please explain in what cases df = n and why...

I cannot find anything on the internet

thank you