Reconsider the experiment in Problem 3-1. Find a 95 percent confidence interval on the mean tensile strength of the portland cement produced by each of the four mixing techniques. Also find a 95 percent confidence interval on the difference in means for techniques 1 and 3. Does this aid you in interpreting the results of the experiment?

Problem 3-1

The tensile strength of portland cement is being studied. Four different mixing techniques can be used economically. The following data have been collected:

 

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Mixing Technique Tensile Strength (lb/in?) 1 3129 3000 2865 2890 2 3200 3300 2975 3150 2800 2900 2985 3050 4 2600 2700 2600 2765