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## Homework Statement

Trials of a biology experiment are performed, and each trial is independent of the other

trials. Each experiment trial has a 0.13 probability of a success, and 0.87 probability of

failure.

(c) Let Y denote the random variable representing the number of trials up to and including

the first success. Find an expression for the probability distribution of Y ,

then use MATLAB to compute and plot this function for the first 50 possible values.

(d) Let Y be defined as in (c). Find an expression for and use MATLAB to compute

Pr(Y < 9).

(e) Let Y be defined again as in (c). Find a mathematical expression for and compute

(using MATLAB) the probability that Y is less than or equal to 12 given that Y is

greater than 8.

## Homework Equations

n/a

## The Attempt at a Solution

is part(c) just

Pr(Y=y) = 0.87^(y-1)*0.13

part(d)

Pr(Y<9) = [tex]\sum(0.87^(y-1)*0.13[/tex]

and got no idea for part (e), need help please.