A software house wished to study the effect of four different methods of teaching on the proficiency of individuals creating tax return reports (how fast users can make their reports), i.e. by using their tax return software application.  The methods used were A) verbal cues B)  verbal cues and video taped feed back C) video taped feed back D) the control treatment (neither verbal cues nor video taped feed back).  A group of 24 first-timers (who had never made a tax return report), was randomly divided into four groups of six subjects each.  Each group of subjects was taught using one of the four methods, and at the end of the course, each subject was timed while creating a certain tax return report (use 5% tolerance).    If Ho is rejected then Use Tukey to find the teaching method which has the most impact on time to create the tax report. The result is in the following table (in minutes) :   Teaching methods = A-D (four)

H0 :  mu1 = mu2 = mu3 = m4   all means are equal