Math Problem Statement

A computer software firm maintains a telephone hotline service for its customers. The firm finds that 40% of the calls involve questions about the application of the software, 45% involve issues of incompatibility with the hardware, and 15% involve the inability to install the software on the user's machine. These three categories of problems can be resolved with probabilities 0.90, 0.30 and 0.80, respectively. Knowing that an incoming call that does not involves question about the application of the software cannot be resolved, then the probability that it involves issues of incompatibility is

Question 10 Select one:

A. None of the others

B. 0.8182

C. 0.7778

D. 0.9130

Solution

Let's approach the problem using conditional probability.

Problem Summary:

Given the following dataLet's approach the problem using conditional probability.

Problem Summary:

Given the following

  • P(A)=0.40P(A) = 0.40: Probability that a call involves questions about the application of the software.
  • P(B)=0.45P(B) = 0.45: Probability that a call involves issues of incompatibility with hardware.
  • P(C)=0.15P(C) = 0.15: Probability that a call involves the inability to install the software.

The probabilities that these categories can be resolved are:

  • P(ResolvedA)=0.90P(\text{Resolved} \mid A) = 0.90
  • P(ResolvedB)=0.30P(\text{Resolved} \mid B) = 0.30
  • P(ResolvedC)=0.80P(\text{Resolved} \mid C) = 0.80

We also know that if an incoming call does not involve questions about the application of the software (i.e., it’s either about hardware incompatibility or installation issues), it cannot be resolved.

Objective:

To find the probability that a call involves issues of incompatibility with hardware given that it does not involve questions about the application of the software and cannot be resolved.

This can be represented as:

P(BNot A and Not Resolved)P(B \mid \text{Not } A \text{ and Not Resolved})

Step 1: Determine the Probability of "Not A"

The probability that a call does not involve questions about the application of the software is:

P(Not A)=1P(A)=10.40=0.60P(\text{Not } A) = 1 - P(A) = 1 - 0.40 = 0.60

Step 2: Determine the Conditional Probabilities for "Not Resolved" Given BB and CC

  • P(Not ResolvedB)=10.30=0.70P(\text{Not Resolved} \mid B) = 1 - 0.30 = 0.70
  • P(Not ResolvedC)=10.80=0.20P(\text{Not Resolved} \mid C) = 1 - 0.80 = 0.20

Step 3: Apply the Law of Total Probability for P(Not ResolvedNot A)P(\text{Not Resolved} \mid \text{Not } A)

Since "Not A" includes both categories BB and CC:

P(Not ResolvedNot A)=P(B)P(Not ResolvedB)+P(C)P(Not ResolvedC)P(Not A)P(\text{Not Resolved} \mid \text{Not } A) = \frac{P(B) \cdot P(\text{Not Resolved} \mid B) + P(C) \cdot P(\text{Not Resolved} \mid C)}{P(\text{Not } A)}

Substituting the values:

P(Not ResolvedNot A)=(0.45×0.70)+(0.15×0.20)0.60P(\text{Not Resolved} \mid \text{Not } A) = \frac{(0.45 \times 0.70) + (0.15 \times 0.20)}{0.60}

P(Not ResolvedNot A)=0.315+0.030.60=0.3450.60=0.575P(\text{Not Resolved} \mid \text{Not } A) = \frac{0.315 + 0.03}{0.60} = \frac{0.345}{0.60} = 0.575

Step 4: Calculate P(BNot A and Not Resolved)P(B \mid \text{Not } A \text{ and Not Resolved})

Using Bayes’ Theorem:

P(BNot A and Not Resolved)=P(B)P(Not ResolvedB)P(Not ResolvedNot A)P(B \mid \text{Not } A \text{ and Not Resolved}) = \frac{P(B) \cdot P(\text{Not Resolved} \mid B)}{P(\text{Not Resolved} \mid \text{Not } A)}

Substituting the values:

P(BNot A and Not Resolved)=0.45×0.700.575=0.3150.5750.5478P(B \mid \text{Not } A \text{ and Not Resolved}) = \frac{0.45 \times 0.70}{0.575} = \frac{0.315}{0.575} \approx 0.5478

Step 5: Interpret the Answer Options

Since none of the provided answer choices match 0.54780.5478, the correct choice would be:

A. None of the others


Would you like further details or have any other questions? Here are 5 related questions to explore:

  1. How does conditional probability apply to real-world scenarios?
  2. What is the Law of Total Probability and when is it used?
  3. Can you explain the significance of Bayes' Theorem?
  4. How would the solution change if different resolution probabilities were given?
  5. What if there were additional categories of customer problems?

Tip: When dealing with probability problems, always clearly define the conditions and categories involved before applying formulas.

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Math Problem Analysis

Mathematical Concepts

Probability
Conditional Probability
Bayes' Theorem
Law of Total Probability

Formulas

Bayes' Theorem

Theorems

Law of Total Probability

Suitable Grade Level

Advanced High School / College