English subtitles

← 18-13 Summarize_2_Solution

18-13 Summarize_2_Solution

Get Embed Code
3 Languages

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

  1. The mean is obviously 25.
  2. In fact, every element over here is 5 times as large as any element over here.
  3. Now, how does this affect the variance?
  4. Well, when we compute the differences from the mean, they're going to be 5 times as large.
  5. When we square them, they will be 25 times as large.
  6. As a result, the variance is 25 times as large as over here--it's 50.
  7. And we can quickly check this.
  8. Obviously, there is no difference for 25 in the middle.
  9. 20 and 25 are 5 apart--the square of this is 25.
  10. Same for 30. 15 and 25 are 10 apart. The square is 100.
  11. We add those up--we get 250--and now we divide by 5 to get back our 50.
  12. The standard deviation is 7.071,
  13. and that's exactly 5 times as large as the standard deviation over here.
  14. If this is 25 times as large as this one,
  15. then the square root of it will be just 5 times as large as this one.
  16. You can easily verify that this is the square root of 50.