The tensile strength of portland cement is being studied. Four different mixing techniques can be used economically. The following data have been collected: (a) Test the hypothesis that mixing techniques affect the strength of the cement. Use α=0.05 (b) Construct a graphical display as described in Section 3-5.3 to compare the mean tensile strengths for the four mixing techniques. What are your conclusions? (c) Use the Fisher LSD method with α=0.05 to make comparisons between pairs of means. (d)