HW-Worksheet
Ch. 8 Test THURSDAY 1-9-14
www.westex.org HS, Teacher Website
1-7-14
Warm up—AP Stats
Repeat of yesterday’s warm up with a twist...
Mr. Lerner is a 60% free throw shooter. What is
the chance that his first made free throw comes
after his 5th shot? Let’s now use GEOCDF to solve
this problem….
1. Construct a probability distribution table for X = number of rolls of a die until a 5 occurs.
X
P(X)
1
2
3
4
5
6
7
2. Construct the probability histogram that corresponds with your table from #1.
8.45 Flip a Coin-Flip a coin until a head appears.
8
a. Indentify the random variable X.
b. Construct the pdf table for X. Then plot the probability histogram.
c. Add on to your pdf table
with a row for cdf.
8.46 Arcade Game-Glenn likes the game at the state fair where you toss a coin into a saucer.
You win if the coin comes to rest in the saucer without sliding off. Glen has played this game
many times and has determined that on average he wins 1 out of every 12 times he plays. He
believes that his chances of winning are the same for each toss. He has no reason to think that
his tosses are not independent. Let X be the number of tosses until a win. Glenn believes that
this describes a geometric setting.
a. Use the formula for calculating P(X > n) to find the probability that it takes more than 10
tosses until Glenn wins a stuffed animal.
b. Find the answer to a. by calculating the probability of the complement: 1 – P(X ≤ 10).
8.48 Language Skills-The State Department is trying to identify an individual who speaks Farsi
to fill a foreign embassy position. They have determined that 4% of the applicant pool are
fluent in Farsi.
a. If applicants are contacted randomly, how many individuals can they expect to interview in
order to find one who is fluent in Farsi?
b. What is the probability that they will have to interview more than 25 until they find one who
speaks Farsi? More than 40?
8.49 Shooting free throws-A basketball player makes 80% of her free throws. We put her on
the free-line and ask her to shoot free throws until she misses one. Let X = the number of free
throws the player takes until she misses.
a. What assumptions do you need to make in order for the geometric model to apply? What
action constitutes “success” in this context?
b. What is the probability that the player will make 5 shots before she misses?
c. What is the probability that she will make at most 5 shots before she misses?