How does the t test work?
First, you will calculate the means and standard deviations for each group. You might use a computer to do all of this for you.

Next, you will use the t test formula to compute the t-value. The formula you use will depend on whether you have equal numbers of subjects, the standard deviations are not different, or if you are testing the same people twice or using matched groups.

The t-score is like a z-score and tells you if the difference is far away from the center of a distribution. In this case, the distribution is the sampling distribution of differences.

If the t-value is big enough (you look it up in a t-table), you will reject the Null Hypothesis and say you have a difference. If it is not big enough, you will say that you have not found a difference and fail to reject the Null Hypothesis.