Consider three observations $a, b,$ and $c$ such that $b = a + c$. If the standard deviation of $a + 2, b + 2, c + 2$ is $d$,then which of the following holds true?

  • A
    $b^2 = 3(a^2 + c^2 + d^2)$
  • B
    $b^2 = a^2 + c^2 + 3d^2$
  • C
    $b^2 = 3(a^2 + c^2) - 9d^2$
  • D
    $b^2 = 3(a^2 + c^2) + 9d^2$

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