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← 18-08 Standard_Deviation_1

18-08 Standard_Deviation_1

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

  1. So coming back to our example, here are the variances again.
  2. Let me give you another word that's really important called standard deviation.
  3. The variance by its very nature computes in the quadratic.
  4. It's the quadratic deviation from the mean.
  5. In fact, it's the average quadratic deviation from the mean.
  6. If you don't want something quadratic, then you can take the square root of it,
  7. and you get what's called the standard deviation.
  8. In the first case √0.8 is 0.8944, and second case the √148.4 is about 12.18.
  9. This is how much you expect the age of an individual family member to deviate
  10. from the mean by about 12 years.
  11. Whereas here you expect the deviation to be just below 1 year.
  12. You can see why this is a good approximation.
  13. Here 4 of the 5 kids differ in age by 1 yr
  14. whereas here people differ as much as 20 years in age from the mean.
  15. The variance and the standard deviation are much larger.
  16. Let's practice this.
  17. I'll give you a couple of quizzes now.
  18. I'll give you data. I want you to complete the mean for me, the variance and the standard deviation.
  19. 3, 4, 5, 6, 7--please fill in all three of those values.