# Powerpoint

```Chapter 8 Day 5
Homework Solutions
17.
A) X = number of hard drives tested until the first defective
B) .0266
C) table
18.
On calculator
19.
B) .3349
20.
A) success = missed shot
C) .7379
21.
A) geometric; X = number of draws until red is chosen
B) .2449; .8163; .1837
C) k = 26
B) .0655
Mean of Geometric Distribution

The mean of a geometric distribution is found using the
formula:
1

p
where p is the probability of success

Recall, the mean is also called the expected value!
Example

Aaron’s love potion works on 90% of women. What is the
expected number of girls that it will take before the love
potion fails?
Example

Suppose Roberto, a well-known major league baseball
player finished last season with a .325 batting average. He
wants to calculate the probability that he will get his first
hit of the new season in his first at-bat.You define a
success as getting a hit and define the random variable X
= number of at-bats until Roberto gets his first hit.

Roberto wants to know the expected number of at bats
until he gets a hit. What would you tell him?
```
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