written 6.0 years ago by | modified 2.9 years ago by |
Hence find its variance and mean.
written 6.0 years ago by | modified 2.9 years ago by |
Hence find its variance and mean.
written 6.0 years ago by |
Solution:
i) Moment Generating Function (M.G.F.)
The M.G.F. about the origin is:
M0(t)=E(etx)=∑p(x)etx=∑∞x=0e−mmxx!.etx=e−m∑∞x=0(met)xx!=e−m.emet
∴M0(t)=em(et−1)
ii) Mean and Variance of Poisson Distribution
μ′1=E(x)=∑pixi=∑∞x=0e−mmxx!x=∑∞x=1e−mmx(x−1)!=me−m∑∞x=1m(x−1)(x−1)!
μ′1=me−m[1+m+m22!+m33!+−−−−]=me−m.em=m
∴ Mean =μ′1=m
μ′2=E(x2)=∑pix2i=∑∞x=0e−m.mxx!x2
∴x2=x+x(x−1)
μ′2=∑∞x=0e−m.mxx![x+x(x−1)]=∑∞x=0e−m.mx.xx!+∑∞x=0e−m.mx.x(x−1)x!
μ′2=me−m∑∞x=1mx−1(x−1)!+m2e−m∑∞x=2mx−2(x−2)!
μ′2=me−m.em+m2e−m[1+m1!+m22!+−−−−]
μ′2=me−m.em+m2e−m.em=m+m2
μ2=μ′2−μ′1=m+m2−m2=m
∴ Variance=μ2=m