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← 26-14 Golf_4_Solution

26-14 Golf_4_Solution

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Showing Revision 2 created 11/02/2015 by Udacity Robot.

  1. This was a trick question, which was totally nontrivial.
  2. Multiplying something with A+b modifies the mean in a very straightforward way.
  3. So this is the valid expression here, aµ+b. So 6 would've been the right answer over here.
  4. You already know that adding a constant doesn't change the spread of a distribution.
  5. So the result should not have a b inside. That takes out this term and all those terms.
  6. We also know that the spread has nothing to do with the mean so this term is out.
  7. So the question really is, is it aσ² or a²σ²?
  8. And if you remember correctly when we did the salary raise by a factor of 10%,
  9. we noticed that the standard deviation goes up by this factor.
  10. Therefore, the variance goes up by the square of this factor
  11. and 1 is the right answer here and not 7.
  12. And that's interesting because in doing arithmetic with the mean and the variance,
  13. you have to be very conscientious as to whether you use the variance or the standard deviation.
  14. If you get that wrong, then you've got the wrong answer.