A physics instructor believes that natural lighting in classrooms improves student learning. He conducts an experiment in which he teaches the same physics unit to two groups of seven randomly assigned students in each group. Everything is similar for the groups, except that one of the groups receives the instruction in a classroom that admits a lot of natural light in addition to the incandescent lighting while the other uses a classroom with only incandescent lighting. At the end of the unit, both groups are given the same end-of-unit exam. There are 20 possible points on the exam; the higher the score, the better the performance. The following scores are obtained.

Natural Plus Incandescent Lighting	Incandescent Lighting Only
16	17
18	15
14	10
19	12
16	15
20	15
17	14

Using ???? = 0.05_{2 tail}, what do you conclude?

tobt	=
tcrit	= ±