## ← 30-41 Variance_Proof_1

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30-41 Variance_Proof_1

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

1. Here's a game I would like to play with you.
2. I drew on the right side six different expressions, and I'm going to derive this for you,
3. leaving out those six expressions and whenever I stop, you have to pick one on the right side,
4. Click the appropriate radio button--or maybe two of them--and if they're correct, we'll move on.
5. To calculate the variance of x, we first notice that p is the mean of x,
6. and if you look at the two possible outcomes starting with heads and then tails,
7. you find that the probability for heads is p and if heads is chosen
8. then the variance is the quadratic difference of the actual outcome,
9. which is 1 for heads minus the mean which equals p.
10. Complete the same expression for the tails case.
11. What's the probability of tails, and if tails actually occurs, the outcome is 0.
12. What will be the quadratic deviation we putt into this formula over here?