USING R PROGRAM An experiment was conducted to determine the effect of four factors on the resistivity of a semiconducto

[answerhappygod]

USING R PROGRAM
An experiment was conducted to determine the effect of four
factors on the resistivity of a semiconductor wafer. The data is
found in wafer where each of the four factors is coded as - or +
depending on whether the low or the high setting for that factor
was used. Fit the linear model 𝑟𝑒𝑠𝑖𝑠𝑡 ~𝑥1+𝑥2+𝑥3+𝑥4.
a. Extract the 𝑋 matrix using the model.matrix function. Examine
this to determine how the low and high levels have been coded in
the model.
b. Compute the correlation in the 𝑋 matrix. Why are there some
missing values in the matrix?
c. What difference in resistance is expected when moving from the
low to the high level of 𝑥1?
d. Refit the model without 𝑥4 and examine the regression
coefficients and standard errors? What stayed the same as the
original fit and what changed?
e. Explain how the change in the regression coefficients is related
to the correlation matrix of 𝑋.