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Dan's Diner employs three dishwashers. Al washes \(40 \%\) of the dishes and breaks only \(1 \%\) of those he handles. Betty and Chuck each wash \(30 \%\) of the dishes, and Betty breaks only \(1 \%\) of hers, but Chuck breaks \(3 \%\) of the dishes he washes. (He, of course, will need a new job soon. ...) You go to Dan's for supper one night and hear a dish break at the sink. What's the probability that Chuck is on the job?

Short Answer

Expert verified
The probability that Chuck is on the job is approximately 56.25%.

Step by step solution

01

Determine the Probabilities per Dishwasher

Identify the percentage of dishes each dishwasher is responsible for. Al washes \(40\%\), while Betty and Chuck handle \(30\%\) each. Also, note their respective breakage rates: Al and Betty each break \(1\%\) of their dishes, and Chuck breaks \(3\%\).
02

Calculate the Probability of Breaking a Dish

Calculate the probability that a given dishwasher breaks a dish, using the formula: \( P(B) = P(A) \times P(B|A) \). For Al: \(0.4 \times 0.01 = 0.004\); for Betty: \(0.3 \times 0.01 = 0.003\); for Chuck: \(0.3 \times 0.03 = 0.009\).
03

Total Probability of Breaking a Dish

Sum up the probabilities from all the dishwashers to find the total probability of hearing a dish break. So, \(0.004 + 0.003 + 0.009 = 0.016\). This value represents the total probability, \( P(C') \), of a dish breaking.
04

Probability that Chuck Broke the Dish Given a Break Occurred

Apply Bayes' theorem to calculate \( P(C | C') \). Use the formula: \[ P(C | C') = \frac{P(C') \cdot P(C'|C)}{P(C')} = \frac{0.009}{0.016} \approx 0.5625. \] This represents the probability that Chuck broke the dish given that a dish was heard to break.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Probability
Probability is a fundamental concept in statistics and mathematics. It measures the likelihood of a particular event happening. The probability of an event is expressed as a number between 0 and 1. Here, 0 indicates that the event will not occur, and 1 indicates certainty that the event will or has already occurred.
  • If an event is impossible, its probability is \( 0 \).
  • If an event is certain, its probability is \( 1 \).
  • The probability of all possible outcomes of a random experiment must sum up to \( 1 \).
In Dan's Diner exercise, each dishwasher (Al, Betty, and Chuck) has a certain percentage of the dishes they wash.This is a basic application of probability, where each dishwasher's duty accounts for a certain fraction of the work.Understanding these basic probabilities helps in further calculations such as determining which dishwasher is more likely to break a dish based on their assigned tasks.
Conditional Probability
Conditional Probability helps us understand the probability of an event occurring, given that another event has already occurred.It is calculated by considering a reduced sample space where the condition has already been met.Mathematically, the conditional probability of event A given event B is expressed as:\[ P(A|B) = \frac{P(A \cap B)}{P(B)} \]In the context of Dan's Diner, we're interested in knowing the probability that a particular dishwasher, such as Chuck, breaks a dish, given that we know a dish has been broken.To calculate this, we need to know both the probability of Chuck working and the probability of a break occurring when he works.For each dishwasher:
  • Determine the probability that they are responsible for handling the dishes.
  • Then, find out the likelihood of them breaking a dish out of their portion of dishes.
This context turns into conditional probabilities, like calculating the 3% chance Chuck may break any dish that he handles.
Bayesian Analysis
Bayesian Analysis is a statistical method that applies Bayes' Theorem to update the probability of a hypothesis as more evidence becomes available.In simple terms, it's a way to revise existing predictions or beliefs based on new or additional data.Bayes’ Theorem is given by:\[ P(A|B) = \frac{P(B|A) \cdot P(A)}{P(B)} \]This theorem allows us to swap the effects of a condition. For example, it allows us to exchange the roles of cause and effect to find the probability of a cause given the effect.In Dan's Diner scenario, we use Bayesian Analysis to find the probability of Chuck being responsible for a broken dish, given that a dish has been broken.Steps in this analysis include:
  • Calculating the total probability of the event (in this case, a break happening).
  • Considering individual probabilities of break incidences due to each dishwasher.
  • Updating the beliefs (probabilities) accordingly to focus on Chuck due to the high break rate of 3% associated with him.
Bayesian Analysis helps us make informed decisions by updating our probability estimates based on the observed evidence, like a dish breaking at Dan’s Diner.

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Most popular questions from this chapter

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