/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 51 Two wine tasters rate each wine ... [FREE SOLUTION] | 91Ó°ÊÓ

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Two wine tasters rate each wine they taste on a scale of 1 to 5. From data on their ratings of a large number of wines, we obtain the following probabilities for both tasters' ratings of a randomly chosen wine: $$ \begin{array}{cccccc} \hline &&& {\text { Taster 2 }} \\ \text { Taster 1 } & 1 & 2 & 3 & 4 & 5 \\ \hline 1 & 0.05 & 0.02 & 0.01 & 0.00 & 0.00 \\ \hline 2 & 0.02 & 0.08 & 0.04 & 0.02 & 0.01 \\ \hline 3 & 0.01 & 0.04 & 0.25 & 0.05 & 0.01 \\ \hline 4 & 0.00 & 0.02 & 0.05 & 0.18 & 0.02 \\ \hline 5 & 0.00 & 0.01 & 0.01 & 0.02 & 0.08 \\ \hline \end{array} $$ (a) Why is this a legitimate discrete probability model? (b) What is the probability that the tasters agree when rating a wine? (c) What is the probability that Taster 1 rates a wine higher than Taster 2? What is the probability that Taster 2 rates a wine higher than Taster 1 ?

Short Answer

Expert verified
(a) It is legitimate; (b) 0.64; (c) Both are 0.18.

Step by step solution

01

Verify Total Probability

A legitimate probability model requires that the sum of all probabilities equals 1. To confirm this, add up all the given probabilities for each combination of ratings by Taster 1 and Taster 2. Calculate:\[ 0.05 + 0.02 + 0.01 + 0.00 + 0.00 + \]\[ 0.02 + 0.08 + 0.04 + 0.02 + 0.01 + \]\[ 0.01 + 0.04 + 0.25 + 0.05 + 0.01 + \]\[ 0.00 + 0.02 + 0.05 + 0.18 + 0.02 + \]\[ 0.00 + 0.01 + 0.01 + 0.02 + 0.08 = 1.00 \]Hence, the sum of all probabilities is indeed 1, indicating a legitimate probability model.
02

Calculate Probability of Agreement

To find when both tasters agree, we need to add the probabilities where the taster ratings are identical, i.e., where Taster 1's rating equals Taster 2's rating. These are the diagonal elements of the matrix:\[ P(1,1) = 0.05,\ P(2,2) = 0.08,\ P(3,3) = 0.25,\ P(4,4) = 0.18,\ P(5,5) = 0.08 \]Thus, the probability that the tasters agree is:\[ 0.05 + 0.08 + 0.25 + 0.18 + 0.08 = 0.64 \]
03

Calculate Probability of Taster 1 Rating Higher

To determine the probability that Taster 1 rates a wine higher, sum the probabilities where Taster 1's score is greater than Taster 2's:\[ (2,1): 0.02,\ (3,1): 0.01,\ (3,2): 0.04,\ (4,1): 0.00,\ (4,2): 0.02,\ (4,3): 0.05,\ (5,1): 0.00,\ (5,2): 0.01,\ (5,3): 0.01,\ (5,4): 0.02 \]Add these probabilities:\[ 0.02 + 0.01 + 0.04 + 0.00 + 0.02 + 0.05 + 0.00 + 0.01 + 0.01 + 0.02 = 0.18 \]
04

Calculate Probability of Taster 2 Rating Higher

Similarly, to find when Taster 2 rates higher, sum the probabilities where Taster 2's score is greater than Taster 1's:\[ (1,2): 0.02,\ (1,3): 0.01,\ (1,4): 0.00,\ (1,5): 0.00,\ (2,3): 0.04,\ (2,4): 0.02,\ (2,5): 0.01,\ (3,4): 0.05,\ (3,5): 0.01,\ (4,5): 0.02 \]Sum these probabilities as well:\[ 0.02 + 0.01 + 0.00 + 0.00 + 0.04 + 0.02 + 0.01 + 0.05 + 0.01 + 0.02 = 0.18 \]
05

Summarize Results

We now have the results for each part of the problem: - The model is legitimate since the total probability is 1. - Probability that tasters agree is 0.64. - Probability that Taster 1 rates higher is 0.18. - Probability that Taster 2 rates higher is 0.18.

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Key Concepts

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

Discrete Probability Model
In probability theory, a discrete probability model is used to represent scenarios where outcomes are distinct and countable. This particular model is expressed in a probability distribution table, where each cell displays the probability of combined outcomes between two distinct events—here, the ratings by two wine tasters. Each pairing of ratings (i.e., Taster 1 rating 1 paired with Taster 2 rating 4) has a specific probability based on historical data.

To verify this as a legitimate discrete probability model, the sum of all probabilities should be 1. This is crucial because it adheres to the basic axiom of probability, which states that the total probability across all possible outcomes must be 1. In this exercise, summing the probabilities of each rating combination confirms this axiom as they add up to 1. This is often the first step when working with probability distributions: ensuring the model is valid before proceeding to any calculations.
Probability Calculation
Calculating probabilities involves summing specific probabilities based on given conditions. When tasked with finding the probability that both tasters agree, you would sum the probabilities where Taster 1's rating equals Taster 2's rating. These probabilities are found along the diagonal of the probability matrix because each pairing corresponds to both tasters giving identical ratings.

Similarly, calculating the probability of one taster rating higher than the other involves selecting the appropriate probabilities from the matrix:
  • For Taster 1 rating higher: sum probabilities where Taster 1's rating exceeds Taster 2's.
  • For Taster 2 rating higher: sum where Taster 2's rating exceeds Taster 1's.
This structured approach not only adheres to systematic probability rules but also ensures that no potential outcome is overlooked, making your calculations accurate and comprehensive.
Probability Theory
Probability theory underpins the understanding of statistical likelihood of events. It encompasses the foundational principles that allow us to make sense of probabilities in structured formats like this exercise.

In this rating exercise, probability theory helps to compute and justify the outcomes based on empirically gathered data. Through it, you can understand events like agreement (where probabilities are individually accumulated to reflect both tasters providing the same score), or comparisons (which show how often one taster rates higher than the other).

Thinking probabilistically requires understanding the distinction between independent probabilities (where outcomes do not affect each other) and dependent probabilities. Testing the sum equals one highlights how they function together across all possible scenarios, a fundamental axiom within probability theory. This deeper understanding aids in analyzing real-world situations quantitatively and qualitatively using probabilistic perspectives.

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Most popular questions from this chapter

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