Dependent groups can be the same subjects used again same measures, or
it can be matched samples. n addition , the t-test is performed on the
difference scores and amounts to little more than a single sample t-test. A
normal distribution of various scores is strongly encouraged, unless the
sample is large enough that you can hide behind the central limit theorem and
claim a normal sampling distribution of means of the differences (in which case
the t-test is robust)there is table used to calculate this at the end.