Mixing technique in Exercise 13-7. Use α = 0.05.

(a) Apply Fisher€™s LSD method with α = 0.05 and determine which levels of the factor differ.

(b) Use the graphical method to compare means described in this section and compare your conclusions to those from Fisher€™s LSD method.

Exercise 13-7

The compressive strength of concrete is being studied, and four different mixing techniques are being investigated.

The following data have been collected.

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Mixing Technique 1 Compressive Strength (psi) 3000 2865 2975 3300 2900 2985 2700 3129 3200 2800 2600 2890 3150 3050 2765 3 4 2600