(Requires Stats Tools) Run a series of multiple regressions of Y versus the X's as follows. Start with an equation that has all of the X's. Then if any X has a p-value greater than 0.05, run another regression without the variable that has the largest p-value. Keep running regressions, always deleting the variable with the largest p-value, until all of the remaining p-values are less than 0.05. Which of the following is true?

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a. The final equation contains 7 of the 8 X's, and the only variable missing has a correlation less than 0.25 (in magnitude) with Y.

b. The final equation has a standard error of estimate greater than the standard error of estimate for the equation with all of the X's, but the difference is less than 0.10.

c. The final equation has an R-square value greater than the R-square value for the equation with all of the X's, but the difference is less than 0.001.

d. All of these choices are true