Probability generating function of a discrete variate process with binomial thinning

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An $mathbfAR(1)$ is given as:



$X_t = alpha * X_t-1 + Z_t $



If $X_T$ is a discrete r.v and $Z_t $ cannot be independent of $X_t-1$, we use the scalar multiplication to denote the binomial thinning.



$X_t = alpha * X_t-1 +z_T $



I want to prove its probability density function as



$P_z(s)=E(s^z) = P_x(s)/P_x(1-alpha + alpha s)$



I stared as follows:



Specifying $z_t$:



$Z_t = X_t - alpha * X_t-1$



$E(S^z_t) = fracE(s^X_t)E(s^alpha X_t-1) = fracE(s^X_t)E(s^alpha s^X_t-1) $



The numerator seems to resemble to the proof, but what about the denominator?







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  • You can get displayed equations by enclosing the in double instead of single dollar signs. That makes them a lot easier to read, especially when you mix fractions, exponents and subscripts.
    – joriki
    Aug 27 at 5:14














up vote
0
down vote

favorite












An $mathbfAR(1)$ is given as:



$X_t = alpha * X_t-1 + Z_t $



If $X_T$ is a discrete r.v and $Z_t $ cannot be independent of $X_t-1$, we use the scalar multiplication to denote the binomial thinning.



$X_t = alpha * X_t-1 +z_T $



I want to prove its probability density function as



$P_z(s)=E(s^z) = P_x(s)/P_x(1-alpha + alpha s)$



I stared as follows:



Specifying $z_t$:



$Z_t = X_t - alpha * X_t-1$



$E(S^z_t) = fracE(s^X_t)E(s^alpha X_t-1) = fracE(s^X_t)E(s^alpha s^X_t-1) $



The numerator seems to resemble to the proof, but what about the denominator?







share|cite|improve this question




















  • You can get displayed equations by enclosing the in double instead of single dollar signs. That makes them a lot easier to read, especially when you mix fractions, exponents and subscripts.
    – joriki
    Aug 27 at 5:14












up vote
0
down vote

favorite









up vote
0
down vote

favorite











An $mathbfAR(1)$ is given as:



$X_t = alpha * X_t-1 + Z_t $



If $X_T$ is a discrete r.v and $Z_t $ cannot be independent of $X_t-1$, we use the scalar multiplication to denote the binomial thinning.



$X_t = alpha * X_t-1 +z_T $



I want to prove its probability density function as



$P_z(s)=E(s^z) = P_x(s)/P_x(1-alpha + alpha s)$



I stared as follows:



Specifying $z_t$:



$Z_t = X_t - alpha * X_t-1$



$E(S^z_t) = fracE(s^X_t)E(s^alpha X_t-1) = fracE(s^X_t)E(s^alpha s^X_t-1) $



The numerator seems to resemble to the proof, but what about the denominator?







share|cite|improve this question












An $mathbfAR(1)$ is given as:



$X_t = alpha * X_t-1 + Z_t $



If $X_T$ is a discrete r.v and $Z_t $ cannot be independent of $X_t-1$, we use the scalar multiplication to denote the binomial thinning.



$X_t = alpha * X_t-1 +z_T $



I want to prove its probability density function as



$P_z(s)=E(s^z) = P_x(s)/P_x(1-alpha + alpha s)$



I stared as follows:



Specifying $z_t$:



$Z_t = X_t - alpha * X_t-1$



$E(S^z_t) = fracE(s^X_t)E(s^alpha X_t-1) = fracE(s^X_t)E(s^alpha s^X_t-1) $



The numerator seems to resemble to the proof, but what about the denominator?









share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Aug 25 at 7:52









Tos Hina

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1,027418











  • You can get displayed equations by enclosing the in double instead of single dollar signs. That makes them a lot easier to read, especially when you mix fractions, exponents and subscripts.
    – joriki
    Aug 27 at 5:14
















  • You can get displayed equations by enclosing the in double instead of single dollar signs. That makes them a lot easier to read, especially when you mix fractions, exponents and subscripts.
    – joriki
    Aug 27 at 5:14















You can get displayed equations by enclosing the in double instead of single dollar signs. That makes them a lot easier to read, especially when you mix fractions, exponents and subscripts.
– joriki
Aug 27 at 5:14




You can get displayed equations by enclosing the in double instead of single dollar signs. That makes them a lot easier to read, especially when you mix fractions, exponents and subscripts.
– joriki
Aug 27 at 5:14















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