An article in the Materials Research Bulletin (Vol. 26, No. 11, 1991) investigated four different methods of preparing the superconducting compound PbMo6S8. The authors contend that the presence of oxygen during the preparation process affects the material€™s superconducting transition temperature Tc. Preparation methods 1 and 2 use techniques that are designed to eliminate the presence of oxygen, while methods 3 and 4 allow oxygen to be present. Five observations on Tc (in °K) were made for each method, and the results are as follows:

(a) Is there evidence to support the claim that the presence of oxygen during preparation affects the mean transition temperature? Use a = 0.05.
(b) What is the P-value for the F-test in part (a)?
(c) Analyze the residuals from this experiment.
(d) Find a 95% confidence interval on mean Tc when method 1 is used to prepare the material.

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Preparation Method Transition Temperature T(°K) 14.7 14.9 12.4 14.8 14.6 14.8 14.8 14.9 14.7 2 14.8 15.0 11.6 3 12.7 12.7 12.1 14.4 12.2 14.2 14.4 11.7