※ 引述《std810471 (家程)》之銘言：
: Roll a fair die repeatedly. Let T denote the number of rollings before all 6 sides
: appeared at least once. Compute E(T) and Var(T)
r.vX1~Geo(p=1)
r.vX2~Geo(p=5/6)
r.vX3~Geo(p=2/3)
r.vX4~Geo(p=1/2)
r.vX5~Geo(p=1/3)
r.vX6~Geo(p=1/6)
E(X)=E(X1+X2+X3+X4+X5+X6)
=1+6/5+3/2+2+3+6
=14.7
Var(X)=Var(X1+X2+X3+X4+X5+X6)
=0+6/25+3/4+2+6+30
=38.99
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