2 = p –p - cesgcesg.tamu.edu/wp-content/uploads/2016/02/chap3.pptx.nd_.pdfuniversidade federal de...
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Var(X) = E[X2] – E[X]2 = 12 . P[X=1] – p2
= p – p2 = p(1-p) Exercise!
var(∑ixi)=∑ivar(xi) for independent xi
pe = p if e = 1pe = 1 if e = 0
Result: we have transformed a single categorical variable taking one of m values ai into an m-dimensional numeric variable taking value 1 in the ith column and 0 elsewhere
Bins -> Categorical attributes {a1, a2, a3, a4}
One categorial variable Ai for each possible attribute value ai
= n! / (n1! n2!...nm!) = #ways of choosing m subsets of sizes n1, n2,…,nm
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