# geometric distribution...p.g.f

• March 26th 2011, 02:12 AM
frank567
geometric distribution...p.g.f
hi can any one help with this prblem

Items are bought by individal customers entering a shop and the number of items is a random variable X which has a geometric distribution starting at 0 and has a mean of 4/6.
what is the value of the parameter p of the geometric distribution and what is the p.g.f.(probability generating function ) function of X.

if four customers then visit the shop what is the probability generating function of Y the total amount of items they buy( all items bought are independent of each other 0.

any help , thanks...
• March 26th 2011, 05:45 AM
harish21
For a RV following a geometric distribution, with probability of success p, a mean of 4/6 means $\dfrac{1-p}{p}=\dfrac{4}{6}$

Look at this link for the pgf