a)
below is probability mass function of X:
P(X=1)=P(X<=1)-P(X<1)=1/2-0 =1/2
P(X=3)=P(X<=3)-P(X<3)=2/3-1/2=1/6
P(X=6)=P(X<=6)-P(X<6)=1-2=1/3
b)
x | P(x) | xP(x) | x2P(x) |
1 | 1/2 | 0.500 | 0.500 |
3 | 1/6 | 0.500 | 1.500 |
6 | 1/3 | 2.000 | 12.000 |
total | 3.000 | 14.000 | |
E(x) =μ= | ΣxP(x) = | 3.0000 | |
E(x2) = | Σx2P(x) = | 14.0000 | |
Var(x)=σ2 = | E(x2)-(E(x))2= | 5.000 |
from above expectation =3
and Variance =5
c)
P(4<=X<6)=0 (as no value exist between 4 and 6 for which X has any probabilistic value)
P(1<X<6)=P(X=3)=1/6
d)
E(3X-6X2)=3E(X)-6E(X2)=3*3-6*14=-75
Var(3X-4)=9*Var(X)=9*5=45
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