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← 18-29 Summary

18-29 Summary

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

  1. So the final formula gives us the following, =1/NΣXi²-1/N²(ΣXi)².
  2. And noticed we didn't use any of these elements over here so let me just take them off.
  3. Notice how the calculation of σ² which we're going to rewrite a little bit as follows.
  4. This obviously the same. Noticed how this calculation doesn't rely on this term here anymore.
  5. It solely uses the terms over here. In particular, we have the ΣXi², we have N.
  6. N² is easily calculated from N, and we have ΣXi²--sum them up and when they all summed up,
  7. we find the square of the sum of it--so here the square is outside
  8. and here the square is inside as we sum the elements.
  9. So the counter statistics of ΣXi, ΣXi² and N are sufficient to compute the variance
  10. and the single pass through the data, let's just calculate the variance.