Fifteen trainees in a technical program are randomly assigned to three different types of instructional approaches, all of which are concerned with developing a specified level of skill in computer-assisted design. The achievement test scores at the conclusion of the instructional unit are reported in the table below, along with the mean performance score associated with each instructional approach (high scores are better than low scores). Use the analysis of variance procedure to test the null hypothesis that the three sample means were obtained from the same population, using the 5 percent level of significance for the test.

Instructional method	Test scores	Total scores	Mean test scores
A 1	86	79	81	70	84	400	80
A 2	90	76	88	82	89	425	85
A 3	82	68	73	71	81	375	75