An experiment was conducted to compare the strength of welds produced by four different welding techniques. Each technique was used to weld five pairs of metal plates. The average strengths for the five welds for each technique were:
Technique: A B C D
69 83 75 71
The estimate of experimental error variance was MSE = 15 with 16 degrees of freedom.
Apply the Tukey method to the data using an overall error rate of 0.05 in order to compare all pairs of treatments. Which treatments produce the same average strength?