Project 31: Geometpdf

Suppose you have a 20% chance of winning a particular game of chance.  You plan to play until you win.  The distribution of games you will play is defined by the geometric distribution with p = .2.

The tree diagram for the first several possibilities is shown below.

If X = the number of games played 

P(X = 1) = .2

P(X = 2) = .8*.2 = .16

P(X = 3) = .8*.8*.2 = .128

P(X = 4) = .8^3*.2 = .1024

X can possibly be any number from 1 to infinity but the probabilities continually decrease.  The sum of all the probabilities for X still must equal 1.

Project 31: The variables 'p' and 'x' have been initialized.

p represents the probability of success on any trial (.2 in the example shown above)

x represents the number of trials needed to obtain the first success. 

Task: Appropriately initialize the value of 'geometpdf' that represents the probability that the number of trials needed is x.

Example: if p = .2 and x = 3, then geometpdf should be .128

**If your code works for 5 test cases, you can enter your e-mail address

Universal Computational Math Methods:

pow(5,2) returns 25.0

abs(-3.0) returns 3

sqrt(49.0) returns 7.0