Silicon-germanium alloys have been used in certain types of solar cells. The paper “Silicon-Germanium Films Deposited by Low-Frequency Plasma-Enhanced Chemical Vapor Deposition” (J. of Material Res., 2006: 88–104) reported on a study of various structural and electrical properties. Consider the accompanying data on x Ge concentration in solid phase

(ranging from 0 to 1) and y Fermi level position (eV):

A scatter plot shows a substantial linear relationship. Here is Minitab output from a least squares fit. [Note: There are several inconsistencies between the data given in the paper, the plot that appears there, and the summary information about a regression analysis.]
The regression equation is Ge conc Analysis of Variance Source DF SS MS F P Regression 1 0.241728 0.241728 44.43 0.000 Error 11 0.059842 0.005440 Total 12 0.301569

a. Obtain an interval estimate of the expected change in Fermi-level position associated with an increase of .1 in Ge concentration, and interpret your estimate.

b. Obtain an interval estimate for mean Fermi-level position when concentration is .50, and interpret your estimate.

c. Obtain an interval of plausible values for position resulting from a single observation to be made when concentration is .50, interpret your interval, and compare to the interval of (b).

d. Obtain simultaneous CIs for expected position when concentration is .3, .5, and .7; the joint confidence level should be at least 97%.