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FRM Part I · FRM Exam Part I · Regression with Multiple Explanatory Variables

In a two-regressor model, the standard error of the slope on X1 is 0.30 when X1 and X2 are correlated with an auxiliary R-squared of 0.75. Holding everything else constant, what would the standard error be if X1 were uncorrelated with X2?

The standard error would be 0.15. The VIF is 1/(1 − 0.75) = 4, which inflates variance fourfold and the standard error by its square root, 2. Dividing 0.30 by 2 gives 0.15. Dividing by 4 would wrongly treat VIF as applying to standard error.

  1. A0.075
  2. B0.150Correct
  3. C0.600
  4. D1.200

Explanation

Variance is inflated by VIF = 1/(1 - 0.75) = 4. Standard error is inflated by the square root of VIF, which is 2. Removing collinearity gives 0.30/2 = 0.15. Option 0.075 divides by 4, forgetting the square root.

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