Once you have a T-value (in a two sample t-test) what do you do with it to determine if u can reject the null?

Question

I have a t-value of 0.84

Answer 1

You check it against your H0 and H1, your hypothesis.

Normally you will have a hypothesis value with your H0.  

Depending on 1 or 2 tailed tests, and the confidence level if the difference from the H0 value is bigger than the confidnce level value then you can reject he null.