# Chapter 8 Day 4 Warm

```
On the chapter 8 math test last year 27% of
students got an A. If there are 45 students that take
the test this year, find the following:

What is the probability that 8 students get an A?

What is the probability that at least 7 students get
an A?

What is the expected number of students that will
get an A? What is the standard deviation?
9. μ = 1.25; σ = .9682
10.
A) μ = 4.5
B) σ = 1.7748
C) σ = 1.1619
11.
A) n = 20; p = .25 B) μ = 5
12.
A) .0687; .9313
B) μ = 2.4; σ = 1.3856
13.
A) on calculator
B) .1821
C) μ = 19.8; σ = .445
14.
A) .1; .9
B) .0999
C) .10001
C) .2023

Geometric probability distribution function:
geometpdf(p,x)

Geometric cumulative distribution function:
geometcdf(p,x)
p is the probability of success
x is the number of trials at which the first
success occurs

Aaron’s love potion works on 90% of women.
What is the probability that the love potion
will fail on the 6th girl he meets?

What about on the 3rd girl?

What is the probability that it takes more
than 4 girls to fail?

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.



A. What is the probability that Roberto will
get a hit on his first at-bat?
What is the probability that it will take him at
most 3 at-bats to get his first hit?
What is the probability that it will take him
more than 4 at-bats to get his first hit?
```