1. 

+ 1. The tensile strength of Portland cement is being studied. Four different mixing techniques can be used economically. A completed randomized experiment was conducted and the following data collected: Tensile strength Mixing techniques 1 3129 3000 2865 2890 2 3200 3300 2975 3150 3 2800 2900 2985 3050 4 2600 2700 2600 2765 a. Test the hypothesis that mixing techniques affect the strength of the cement. Use = 0.05 b. Use the Fisher LSD method with = 0.05 to make comparisons between pair of treatments. Construct a normal probability plot of the residual. c. What conclusion would you draw about the validity of the normality assumption