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Chapter 3: Q3-55E (page 193)

For two independent events, A and B, P (A) = .4 and P(B) = .2 :

a. Find P (A∩B)

b. Find P (A/B)

c. Find P (A∪B)

Short Answer

Expert verified

Answer

  1. 0.08
  2. 0.4
  3. 0.52

Step by step solution

01

Step-by-Step SolutionStep 1: Introduction

There are two occurrences, A and B. If the outcome of the A event has no impact on the outcome of the B, the two occurrences are said to be independent.

P(A∩B)= P(A)×P(B)

02

Find the required probability

Since A and B are independent events.

Therefore,

P (A∩B) = P(A)×P(B)= .4×.2= .08

Hence, the required probability is 0.08.

03

Find the required probability

P (A/B) =P (A∩B)P (B)=.08.2=.4

Hence, the required probability is 0.4.

04

Find the required probability

P (A∪B) = P(A) + P (B)−P(A∩B)= 0.4 + 0.2−0.08= 0.52

Hence, the required probability is 0.52.

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Most popular questions from this chapter

Consider the Venn diagram in the next column, where

P(E1)=0.10,P(E2)=0.05,P(E3)=P(E4)=0.2,P(E5)=0.6,P(E6)=0.3,P(E7)=0.06andP(E8)=0.3

Find each of the following probabilities:

a.P(Ac)b.P(Bc)c.P(Ac∩B)d.P(A∪B)e.P(A∩B)f.P(Ac∩Bc)

g. Are events A and B mutually exclusive? Why?

Working on summer vacation. Is summer vacation a break from work? Not according to a Harris Interactive (July 2013) poll of U.S. adults. The poll found that 61% of the respondents work during their summer vacation, 22% do not work while on vacation, and 17% are unemployed. Assuming these percentages apply to the population of U.S. adults, consider the work status during the summer vacation of a randomly selected adult.

a. What is the Probability that the adult works while on summer vacation?

b. What is the Probability that the adult will not work while on summer vacation, either by choice or due to unemployment?

For two events A and B, suppose P(A)=.7,P(B)=.5,P(A∩B)=04FindP(A∪B).

On-the-job arrogance and task performance. Human Performance (Vol. 23, 2010) published the results of a study that found that arrogant workers are more likely to have poor performance ratings. Suppose that 15% of all full-time workers exhibit arrogant behaviors on the job and that 10% of all full-time workers will receive a poor performance rating. Also, assume that 5% of all full-time workers exhibit arrogant behaviors and receive a poor performance rating. Let A be the event that a full-time worker exhibits arrogant behavior. Let B be the event that a full-time worker will receive a poor performance rating.

a. Are the events A and B mutually exclusive? Explain.

b. Find P(B/A).

c. Are the events A and B independent? Explain.

World Cup soccer match draws. Every 4 years the world’s 32 best national soccer teams compete for the World Cup. Run by FIFA (Fédération Internationale de Football Association), national teams are placed into eight groups of four teams, with the group winners advancing to play for the World Cup. Chance(Spring 2007) investigated the fairness of the 2006 World Cup draw. Each of the top 8 seeded teams (teams ranked 1–8, called pot 1) were placed into one of the eight groups (named Group A, B, C, D, E, F, G, and H). The remaining 24 teams were assigned to 3 pots of 8 teams each to achieve the best possible geographic distribution between the groups. The teams in pot 2 were assigned to groups as follows: the first team drawn was placed into Group A, the second team drawn was placed in to Group B, etc. Teams in pots 3 and 4 were assigned to the groups in similar fashion. Because teams in pots 2–4 are not necessarily placed there based on their world ranking, this typically leads to a “group of death,” i.e., a group involving at least two highly seeded teams where only one can advance.

  1. In 2006, Germany (as the host country) was assigned as the top seed in Group A. What is the probability that Paraguay (with the highest ranking in pot 2) was assigned to Group A?
  2. Many soccer experts viewed the South American teams (Ecuador and Paraguay) as the most dangerous teams in pot 2. What is the probability one of the South American teams was assigned to Group A?
  3. In 2006, Group B was considered the “group of death,” with England (world rank 2), Paraguay (highest rank in pot 2), Sweden (2nd highest rank in pot 3), and Trinidad and Tobago. What is the probability that Group B included the team with the highest rank in pot 2 and the team with one of the top two ranks in pot 3?
  4. In drawing teams from pot 2, there was a notable exception in 2006. If a South American team (either Ecuador or Paraguay) was drawn into a group with another South American team, it was automatically moved to the next group. This rule impacted Group C (Argentina as the top seed) and Group F (Brazil as the top seed), because they already had South American teams, and groups that followed these groups in the draw. Now Group D included the eventual champion Italy as its top seed. What is the probability that Group D was not assigned one of the dangerous South American teams in pot 2?
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