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.

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%.

Transcribed Image Text:

xl 0 .42 .23 .33 .62 .60 .45 .87 .90 .79 1 1 1 62 5361 59 50 .55 59 .31 43 46 .23 .22.19 The regression equation is Fermi pos-0.7217-0.4327 Ge conc S: 0.0737573 R-Sq-80.2% R-Sq(adj ) : 78.4% Analysis of Variance Source Regression 1 0.241728 0.241728 44.43 0.000 Error Total DF MS 11 0.059842 0.005440 12 0.301569