Twenty students randomly assigned to experimental group receive instructional program; 30 in control group do not. After six months, both groups are tested on their knowledge. The experimental group has mean of 38 on the test (with estimated population standard deviation of 3); the control group has mean of 35 (with estimated population standard deviation of 5). Using the .05 level, what should the experimenter conclude? (a) Employ the steps of hypothesis testing, (b) sketch the distributions involved, and (c) describe your answer to someone who is familiar with t test for a single sample but not with t test for independent means.