13.74 Three different instructional techniques are being considered for training mechanics to perform a difficult emissions-reduction adjustment on fuel-injection engines.

Each of 60 mechanics is randomly assigned to receive one of the training techniques. For the 20 trained by technique A, 70% are able to perform the adjustment successfully on the first try. For mechanics trained by techniques B and C, the respective percentages are 50% and 65%. At the 0.05 level, can we conclude that the three techniques are equally effective?