clarifying the different t-tests making the original student t-test a defined class under which all other t-tests classify (dropping the original objective from that class), adding 3 classes and relevant metadata, correction to distribution used in paired t-test, adding a 4 subtypes of contrasts (but more work is needed with respect to parameter and parameter estimate discussion and distinction between contrast vectors or contrast estimates), adding restriction on one/two tail test so they classify under statistical tests