12.44 In pressure sintering of alumina., two important variables controlled by the experimenter are the pressure and time of sintering. An experiment involving two pressures and two times, with three specimens tested on each pressure/time, combination, showed the densities (in v/cc): listed in table below.

a Perform an analysis of variance, constructing appropriate tests for interaction and main effects.Use .
b Estimate the difference between the true densities for specimens sintered for 20 minutes and those sintered for 10 minutes. Use a 95%
confidence coefficient.

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Pressure Time 100 psi 200 psi 10 min. 3.6 3.5 3.3 3.8 3.9 3.8 20 min. 3.4 3.7 3.7 4.1 3.9 4.2