How are $$Sxx=\sum_{i=1}^{n}(x_i−\bar x)^2=\sum_{i=1}^{n}x^2_i−n\bar x^2$$ where $\bar x=\sum_{i=1}^{n} x_i/n$ equivalent?
Any help would be much appreciated,
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Not sure why editing is weird, the i = 1 is meant to be under the summation operator. And x-Bar is not aligned properly. – user366770 Sep 05 '22 at 13:21
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Unfortunately, this is incomprehensible. See the MathJax help at https://stats.stackexchange.com/editing-help for how to make your formulas readable. – whuber Sep 05 '22 at 13:23
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There is nothing noble here. Just expand the square. See what happens. – User1865345 Sep 05 '22 at 13:34
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how do you expand brackets of a series?, tried it for a simple case (1,2,3) but cant see algebraically why it works. – user366770 Sep 05 '22 at 13:39
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First multiply out the brackets using the binomial formula. Then apply the sum to each term separately. – Christoph Hanck Sep 05 '22 at 14:03