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Firefighters鈥 use of gas detection devices. Two deadly gasesthat can be present in fire smoke are hydrogen cyanide and carbon monoxide. Fire Engineering (March 2013) reported the results of a survey of 244 firefighters conducted by the Fire Smoke Coalition. The purpose of the survey was to assess the base level of knowledge of firefighters regarding the use of gas detection devices at the scene of a fire. The survey revealed the following: Eighty percent of firefighters had no standard operating procedures (SOP) for detecting/monitoring hydrogen cyanide in fire smoke; 49% had no SOP for detecting/monitoring carbon monoxide in fire smoke. Assume that 94% of firefighters had no SOP for detecting either hydrogen cyanide or carbon monoxide in fire smoke. What is the probability that a firefighter has no SOP for detecting hydrogen cyanide and no SOP for detecting carbon monoxide in fire smoke?

Short Answer

Expert verified

The probability is 0.35.

Step by step solution

01

Given information

According to the information,

A=No. SOP for detecting hydrogen cyanide in fire smoke.

B=No. SOP for detecting carbon monoxide in fire smoke.

PA=80%=0.8PB=49%=0.49PAorB=94%=0.94

The formula for probabilityPNumberoffavourableoutcomesTotalnumberofoutcomes.

The general addition rule for two eventsP(AorB)=P(A)+P(B)-P(AandB).

02

Find the probability

PA=80%=0.8PB=49%=0.49PAorB=PA+PB-PAandBPAandB=PA+PB-PAandB=0.8+0.49-0.94=0.35=35%

Therefore,the probability is 0.35

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Most popular questions from this chapter

Guilt in decision making.Refer to the Journal of Behavioral Decision Making(January 2007) study of theeffect of guilt emotion on how a decision maker focuseson a problem, Exercise 3.48 (p. 183). The results (numberresponding in each category) for the 171 study participantsare reproduced in the table below. Suppose one of the 171participants is selected at random.

Emotional

State

Choose

Stated Option

Do Not Choose

Stated Option

Totals

Guilt

Anger

Neutral

45

8

7

12

50

49

57

58

56

Totals

60

111

171

a.Given that the respondent is assigned to the guilty state, what is the probability that the respondent chooses the stated option?

b.If the respondent does not choose to repair the car, what is the probability that the respondent is in the anger state?

c.Are the events {repair the car} and {guilty state }
independent?

The three-dice gambling problem. According toSignificance(December 2015), the 16th-century mathematician Jerome Cardan was addicted to a gambling game involving tossing three fair dice. One outcome of interest鈥 which Cardan called a 鈥淔ratilli鈥濃攊s when any subset of the three dice sums to 3. For example, the outcome {1, 1, 1} results in 3 when you sum all three dice. Another possible outcome that results in a 鈥淔ratilli鈥 is {1, 2, 5}, since the first two dice sum to 3. Likewise, {2, 3, 6} is a 鈥淔ratilli,鈥 since the second die is a 3. Cardan was an excellent mathematician but calculated the probability of a 鈥淔ratilli鈥 incorrectly as 115/216 = .532.

a. Show that the denominator of Cardan鈥檚 calculation, 216, is correct. [Hint: Knowing that there are 6 possible outcomes for each die, show that the total number of possible outcomes from tossing three fair dice is 216.]

b. One way to obtain a 鈥淔ratilli鈥 is with the outcome {1,1, 1}. How many possible ways can this outcome be obtained?

c. Another way to obtain a 鈥淔ratilli鈥 is with an outcome that includes at least one die with a 3. First, find the number of outcomes that do not result in a 3 on any of the dice. [Hint: If none of the dice can result in a 3, then there are only 5 possible outcomes for each die.] Now subtract this result from 216 to find the number of outcomes that include at least one 3.

d. A third way to obtain a 鈥淔ratilli鈥 is with the outcome {1, 2, 1}, where the order of the individual die outcomes does not matter. How many possible ways can this outcome be obtained?

e. A fourth way to obtain a 鈥淔ratilli鈥 is with the outcome {1, 2, 2}, where the order of the individual die outcomes does not matter. How many possible ways can this outcome be obtained?

f. A fifth way to obtain a 鈥淔ratilli鈥 is with the outcome {1, 2, 4}, where the order of the individual die outcomes does not matter. How many possible ways can this outcome be obtained? [Hint:There are 3 choices for the first die, 2 for the second, and only 1 for the third.]

g. A sixth way to obtain a 鈥淔ratilli鈥 is with the outcome {1, 2, 5}, where the order of the individual die outcomes does not matter. How many possible ways can this outcome be obtained? [See Hintfor part f.]

h. A final way to obtain a 鈥淔ratilli鈥 is with the outcome {1, 2, 6}, where the order of the individual die outcomes does not matter. How many possible ways can this outcome be obtained? [See Hintfor part f.]

i. Sum the results for parts b鈥揾 to obtain the total number of possible 鈥淔ratilli鈥 outcomes.

j. Compute the probability of obtaining a 鈥淔ratilli鈥 outcome. Compare your answer with Cardan鈥檚.

Two fair dice are tossed, and the following events are defined:

A: {Sum of the numbers showing is odd.}

B: {Sum of the numbers showing is 9, 11, or 12.}

Are events A and B independent? Why?

Two fair dice are tossed, and the face on each die is observed.

  1. Use a tree diagram to find the 36 sample points contained in the sample space.
  2. Assign probabilities to the sample points in part a.
  3. Find the probability of each of the following events:

A = {3showing on each die}

B = {Sum of two numbers showing is}

C = {Sum of two numbers showing is even}

A pair of fair dice is tossed. Define the following events:

A: [Exactly one of the dice shows a 1.]

B: [The sum of the numbers on the two dice is even.]

a. Identify the sample points in the events A,B,AB,AB,andAc.

b. Find the probabilities of all the events from part a by summing the probabilities of the appropriate sample points.

C. Using your result from part b, explain why A and B are not mutually exclusive.

d. Find P(AB) using the additive rule. Is your answer the same as in part b?

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