Decide which probability distribution binomial, geometric, or Poisson applies to the question. You do nto need to answer the question. Instead justify your choice.

Telephone Sales: Assume the probability that you will make a sale on any given telephone call is 0.19. Find the probability that you (a) make your first sale on the fifth call, (b) make your first sale on the first, second, or third call, and (c) do not make a slae on the first three calls.

For this particular type of questions we use Geometric Probability Distribution.

Geometric distribution is a probability model and statistical data that is used to find out the number of failures which occurs before single success.

And here similar things are asked: eg. make your first sale on the fifth call, means first 4 calls were not converted, so on and so forth.

Formula :

P(x) = q^{x}p.

Where, p = probability of success for a single trial . q = probability of failure for a single trial ( = 1-p ) x = the number of failures before a success.