For example, in lab assignments where we had different data sets and had to find/use the appropriate test, I went from 98% to 74%.

I don't know what went wrong because we only got back the final grade but not the assignment itself but I think the reason why I got 74% could be due to the fact that I maybe(?) couldn't really distinguish between when to use correlation and when to used t-tests.

I know that correlation is used to find out if/how two variables are related and t-test are used to find out if there is a significant difference between them.

But how do I know which one to use when I get a data set with a question that doesn't ask directly "Is there a significant

*relationship*" etc

Is there a trick to find out which test to use?

Thank you