Probability distribution table help w/ Tree diag .Two values coming strangely.

Hi again.

I'm having a problem with a tree diagram and the subsequent prob.dist.table. Here's the question:

Every day Eduardo tries to phone his friend. Every time he phones there is a 50% chance that his friend will answer. If his friend answers, Eduardo does not phone again on that day. If his friend does not answer, Eduardo tries again in a few minutes’ time. If his friend has not answered after 4 attempts, Eduardo does not try again on that day.

(i) Draw a tree diagram to illustrate this situation.

The figure:

http://usera.ImageCave.com/biosyn/ss.PNG

This is correct.

(ii) Let X be the number of unanswered phone calls made by Eduardo on a day. Copy and complete the table showing the probability distribution of X.

This is what I'm seeing seeing:

x 0 1 2 3 4

P(X=x) 1/2 1/2 1/4 1/8 1/16

But, this seems to be wrong. Once again, I have no clue as to why this is so.

Any help? (Speechless)