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Working on summer vacation.Refer to the Harris Interactive(July 2013) poll of whether U.S. adults workduring summer vacation, Exercise 3.13 (p. 169). Recall thatthe poll found that 61% of the respondents work duringtheir summer vacation, 22% do not work at all while onvacation, and 17% were unemployed. Also, 38% of thosewho work while on vacation do so by monitoring theirbusiness emails.

a.Given that a randomly selected poll respondent will work while on summer vacation, what is the probability that the respondent will monitor business emails?

b.What is the probability that a randomly selected poll respondent will work while on summer vacation and will monitor business emails?

c.What is the probability that a randomly selected poll respondent will not work while on summer vacation and will monitor business emails?

Short Answer

Expert verified
  1. 0.38
  2. 23.18%
  3. 0

Step by step solution

01

 Step 1: Finding the probability that the respondent will monitor business emails while on summer vacation

P(A) = Respondents will monitor business emails = 38% = 0.38

Therefore, the probability that a respondent will monitor business emails while on summer vacation is 0.38.

02

Calculating the probability that the respondent will work during vacation and monitor business emails

P(A) = Respondents will monitor business emails while on vacation = 0.38

P(B) = Respondent will work on summer vacation = 0.61

P(AÇB)=P(A)×P(B)=0.38×0.61=0.2318=23.18%

Hence, the probability that the respondent works during the vacation and monitors email is 23.18%.

03

Finding the probability that a respondent will not work on vacation and monitor emails 

P (A) = Respondent does not work on vacation = 22% = 0.22

P (B) = Respondents monitor emails = 38% = 0.38

The probability of both A and B occurring together is 0because the respondent who does not work at all on vacation will not monitor business emails.

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Most popular questions from this chapter

Drug testing in athletes.When Olympic athletes are tested for illegal drug use (i.e., doping), the results of a single positive test are used to ban the athlete from competition. Chance(Spring 2004) demonstrated the application of Bayes’s Rule for making inferences about testosterone abuse among Olympic athletes using the following example: In a population of 1,000 athletes, suppose 100 are illegally using testosterone. Of the users, suppose 50 would test positive for testosterone. Of the nonusers, suppose 9 would test positive.

  1. Given that the athlete is a user, find the probability that a drug test for testosterone will yield a positive result. (This probability represents the sensitivity of the drug test.)
  2. Given the athlete is a nonuser, find the probability that a drug test for testosterone will yield a negative result. (This probability represents the specificityof the drug test.)
  3. If an athlete tests positive for testosterone, use Bayes’s Rule to find the probability that the athlete is really doping. (This probability represents the positive predictive value of the drug test.)

Randomization in a study of TV commercials. Gonzaga University professors conducted a study of more than 1,500 television commercials and published their results in the Journal of Sociology, Social Work, and Social Welfare (Vol. 2, 2008). Commercials from eight networks—ABC, FAM, FOX, MTV, ESPN, CBS, CNN, and NBC—were sampled for 8 days, with one network randomly selected each day. The table below shows the actual order determined by random draw:

ABC—July 6 (Wed)

FAM—July 7 (Thr)

FOX—July 9 (Sat)

MTV—July 10 (Sun)

ESPN—July 11 (Mon)

CBS—July 12 (Tue)

CNN—July 16 (Sat)

NBC—July 17 (Sun)

a. What is the probability that ESPN was selected on Monday, July 11?

b. Consider the four networks chosen for the weekends (Saturday and Sunday). How many ways could the researchers select four networks from the eight for the weekend analysis of commercials? (Assume that the assignment order for the four weekend days was immaterial to the analysis.)

c. Knowing that the networks were selected at random, what is the probability that ESPN was one of the four networks selected for the weekend analysis of commercials?

Stock market participation and IQ.Refer to The Journal of Finance(December 2011) study of whether the decisionto invest in the stock market is dependent on IQ, Exercise3.46 (p. 182). The summary table giving the number ofthe 158,044 Finnish citizens in each IQ score/investment category is reproduced below. Again, suppose one of the citizens is selected at random.

IQ Score

Invest in Market

No Investment

Totals

1

2

3

4

5

6

7

8

9

893

1,340

2,009

5,358

8,484

10,270

6,698

5,135

4,464

4,659

9,409

9,993

19,682

24,640

21,673

11,260

7,010

5,067

5,552

10,749

12,002

25,040

33,124

31,943

17,958

12,145

9,531

Totals

44,651

113,393

158,044

Source:Based on M. Grinblatt, M. Keloharju, and J. Linnainaa, “IQ and Stock Market Participation,” The Journal of Finance, Vol. 66, No. 6, December 2011 (data from Table 1 and Figure 1).

a.Given that the Finnish citizen has an IQ score of 6 or higher, what is the probability that he/she invests in the stock market?

b.Given that the Finnish citizen has an IQ score of 5 or lower, what is the probability that he/she invests in the stock market?

c.Based on the results, parts a and b, does it appear that investing in the stock market is dependent on IQ? Explain.

Simulate the experiment described in Exercise 3.7 using any five identically shaped objects, two of which are one colour and the three another colour. Mix the objects, draw two, record the results, and then replace the objects. Repeat the experiment a large number of times (at least 100). Calculate the proportion of time events A, B, and C occur. How do these proportions compare with the probabilities you calculated in Exercise 3.7? Should these proportions equal the probabilities? Explain.

An experiment results in one of the following sample points: E1,E2,E3 orE4 . Find PE4for each of the following cases.

  1. PE1=0.1,PE2=0.2,PE3=0.3
  2. PE1=PE2=PE3=PE4
  3. PE1=PE2=0.1andPE3=PE4
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