# geometric distribution

• Nov 13th 2009, 06:38 PM
rosedavis
geometric distribution
Hey, my questions is: Assume the probbilty that yoiu will make a sale on any given phone call is 0.12. find the probability that you (a) will mkae sale on fifth call, (b) make sale on first, second, or third call, and (c) do not make a sale on first three calls.

(a) P(first sale is made on fifth call)=

(b) P(on first,second. or third call)=

(c) P(sale not made in first three calls)=

thank you
• Nov 13th 2009, 08:38 PM
mr fantastic
Quote:

Originally Posted by rosedavis
Hey, my questions is: Assume the probbilty that yoiu will make a sale on any given phone call is 0.12. find the probability that you (a) will mkae sale on fifth call, (b) make sale on first, second, or third call, and (c) do not make a sale on first three calls.

(a) P(first sale is made on fifth call)=

(b) P(on first,second. or third call)=

(c) P(sale not made in first three calls)=

thank you

From the post title, you obviously know about the geometric distribution. Where are you stuck in applying it to (a) and (b)? For (c), the answer is (0.88)^3 (your job is to think about why).
• Nov 14th 2009, 03:43 AM
rosedavis
geometric distribution / finding probability
Thank you Mr. Fantastic. And yes I am stuck in finding a & b.
• Nov 14th 2009, 03:53 AM
mr fantastic
Quote:

Originally Posted by rosedavis
Thank you Mr. Fantastic. And yes I am stuck in finding a & b.

State the formula for a geometric distribution. Define all the symbols in it. Now tell us where you're stuck in using it for (a) and (b) (this is the second time I've asked you to say where you're stuck).

By the way, I suppose I should check this ..... for (a) and (b) do you mean "find the probability that you (a) will mkae first sale on fifth call, (b) make first sale on first, second, or third call" (since the title of the thread is geometric distribution I assume that's the case).