An article in the Materials Research Bulletin investigated four different methods of preparing the superconducting compound PbMo 6 S 8 . The authors contend that the presence of oxygen during the...

An article in the
Materials Research Bulletin
 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
T

_c
. 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
T

_c
(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 α = 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
T

_c
when method 1 is used to prepare the material.