Introductory Statistics 2e

# Bringing It Together: Homework

Introductory Statistics 2eBringing It Together: Homework

117.

A previous year, the weights of the members of the San Francisco 49ers and the Dallas Cowboys were published in the San Jose Mercury News. The factual data are compiled into Table 3.25.

Shirt# ≤ 210 211–250 251–290 290≤
1–33 21 5 0 0
34–66 6 18 7 4
66–99 6 12 22 5
Table 3.25

For the following, suppose that you randomly select one player from the 49ers or Cowboys.

If having a shirt number from one to 33 and weighing at most 210 pounds were independent events, then what should be true about P(Shirt# 1–33|≤ 210 pounds)?

118.

The probability that a person develops cancer is 0.4567. The probability that a person has at least one false positive test result (meaning the test comes back for cancer when the person does not have it) is 0.51. Some of the following questions do not have enough information for you to answer them. Write “not enough information” for those answers. Let C = a person develops cancer and P = a person has at least one false positive.

1. P(C) = ______
2. P(P|C) = ______
3. P(P|C') = ______
4. If a test comes up positive, based upon numerical values, can you assume that a male has cancer? Justify numerically and explain why or why not.
119.

Given events G and H: P(G) = 0.43; P(H) = 0.26; P(H AND G) = 0.14

1. Find P(H OR G).
2. Find the probability of the complement of event (H AND G).
3. Find the probability of the complement of event (H OR G).
120.

Given events J and K: P(J) = 0.18; P(K) = 0.37; P(J OR K) = 0.45

1. Find P(J AND K).
2. Find the probability of the complement of event (J AND K).
3. Find the probability of the complement of event (J OR K).

Use the following information to answer the next two exercises. Suppose that you have eight cards. Five are green and three are yellow. The cards are well shuffled.

121.

Suppose that you randomly draw two cards, one at a time, with replacement.
Let G1 = first card is green
Let G2 = second card is green

1. Draw a tree diagram of the situation.
2. Find P(G1 AND G2).
3. Find P(at least one green).
4. Find P(G2|G1).
5. Are G2 and G1 independent events? Explain why or why not.
122.

Suppose that you randomly draw two cards, one at a time, without replacement.
G1 = first card is green
G2 = second card is green

1. Draw a tree diagram of the situation.
2. Find P(G1 AND G2).
3. Find P(at least one green).
4. Find P(G2|G1).
5. Are G2 and G1 independent events? Explain why or why not.

Use the following information to answer the next two exercises. The percent of licensed U.S. drivers (from a recent year) that are women is 48.60. Of the women, 5.03% are age 19 and under; 81.36% are age 20–64; 13.61% are age 65 or over. Of the licensed U.S. men drivers, 5.04% are age 19 and under; 81.43% are age 20–64; 13.53% are age 65 or over.

123.

Complete the following.

1. Construct a table or a tree diagram of the situation.
2. Find P(driver is a woman).
3. Find P(driver is age 65 or over|driver is a woman).
4. Find P(driver is age 65 or over AND a woman).
5. In words, explain the difference between the probabilities in part c and part d.
6. Find P(driver is age 65 or over).
7. Are being age 65 or over and being a woman mutually exclusive events? How do you know?
124.

Suppose that 10,000 U.S. licensed drivers are randomly selected.

1. How many would you expect to be men?
2. Using the table or tree diagram, construct a contingency table of gender versus age group.
3. Using the contingency table, find the probability that out of the age 20–64 group, a randomly selected driver is a woman.
125.

Approximately 86.5% of Americans commute to work by car, truck, or van. Out of that group, 84.6% drive alone and 15.4% drive in a carpool. Approximately 3.9% walk to work and approximately 5.3% take public transportation.

1. Construct a table or a tree diagram of the situation. Include a branch for all other modes of transportation to work.
2. Assuming that the walkers walk alone, what percent of all commuters travel alone to work?
3. Suppose that 1,000 workers are randomly selected. How many would you expect to travel alone to work?
4. Suppose that 1,000 workers are randomly selected. How many would you expect to drive in a carpool?
126.

When the Euro coin was introduced in 2002, two math professors had their statistics students test whether the Belgian one Euro coin was a fair coin. They spun the coin rather than tossing it and found that out of 250 spins, 140 showed a head (event H) while 110 showed a tail (event T). On that basis, they claimed that it is not a fair coin.

1. Based on the given data, find P(H) and P(T).
2. Use a tree to find the probabilities of each possible outcome for the experiment of tossing the coin twice.
3. Use the tree to find the probability of obtaining exactly one head in two tosses of the coin.
4. Use the tree to find the probability of obtaining at least one head.
127.

Use the following information to answer the next two exercises. The following data represent the number of new vehicles purchased over a monthly time period in a certain county, within two age groups: people in their twenties and people in their thirties.

Sedan SUV Minivan Other Totals
Twenties 1,135 290 583 158
Thirties 1,246 463 241 190
Totals
Table 3.26

Suppose a person from this county is randomly selected.

1. Find P(Person is in their twenties).
2. Find P(Person purchases minivan).
3. Find P(Person is in their twenties OR purchases an SUV).
4. Find P(Person is in their twenties AND purchases a SEDAN).
5. Find P(Person is in their thirties AND purchases an SUV).
6. Find P(Person is in their twenties GIVEN person purchases a minivan).
128.

Answer these questions using probability rules. Do NOT use the contingency table. A total of 6,481 new vehicles were purchased over a monthly time period in a certain county. These purchases will be our population. Of these purchases, 36% were made by people in their twenties, and 42% were purchases of sedans. 20% of purchases were for sedans purchased by people in their twenties.

1. Find P(Person is in their twenties).
2. Find P(Person purchased a sedan).
3. Find P(Person is in their twenties GIVEN person purchased a sedan)