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One method used to distinguish between granitic \((G)\) and basaltic \((B)\) rocks is to examine a portion of the infrared spectrum of the sun's energy reflected from the rock surface. Let \(R_{1}, R_{2}\), and \(R_{3}\) denote measured spectrum intensities at three different wavelengths; typically, for granite \(R_{1}P\) (basalt \(\mid R_{1}<\) \(R_{2}

Short Answer

Expert verified
Classify rocks based on conditional probabilities: \( R_1<R_2<R_3 \) as granite, \( R_1<R_3<R_2 \) as basalt, \( R_3<R_1<R_2 \) as basalt. Erroneous classification probability is 0.1125.

Step by step solution

01

Understanding the Problem Statement

We need to determine the probability distributions for granite and basalt given certain spectral intensity orders. We have prior probabilities for rocks selected as granite and basalt: \( P(\text{granite}) = 0.25 \) and \( P(\text{basalt}) = 0.75 \). We also have conditional probabilities given certain sequences of spectral intensities.
02

Bayes' Theorem Overview

To solve parts (a) and (b), we use Bayes' Theorem: \[P(\text{granite} \mid R_1 < R_2 < R_3) = \frac{P(R_1 < R_2 < R_3 \mid \text{granite}) \times P(\text{granite})}{P(R_1 < R_2 < R_3)}.\] Similarly, apply this theorem to find the probability of basalt given the order \( R_1 < R_2 < R_3 \). We will compute \( P(R_1 < R_2 < R_3) \) using the law of total probability.
03

Calculating Probabilities for Each Order

Compute \( P(R_1 < R_2 < R_3) \):\[P(R_1 < R_2 < R_3) = P(R_1 < R_2 < R_3 \mid \text{granite}) \times P(\text{granite}) + P(R_1 < R_2 < R_3 \mid \text{basalt}) \times P(\text{basalt}) = (0.6 \times 0.25) + (0.1 \times 0.75) = 0.15 + 0.075 = 0.225.\]
04

Applying Bayes' Theorem for Each Case

Compute \( P(\text{granite} \mid R_1 < R_2 < R_3) \) and \( P(\text{basalt} \mid R_1 < R_2 < R_3) \):- \( P(\text{granite} \mid R_1 < R_2 < R_3) = \frac{0.6 \times 0.25}{0.225} = \frac{0.15}{0.225} = \frac{2}{3}. \)- \( P(\text{basalt} \mid R_1 < R_2 < R_3) = \frac{0.1 \times 0.75}{0.225} = \frac{0.075}{0.225} = \frac{1}{3}. \)
05

Classification Based on Given Measurements

For \( R_1 < R_2 < R_3 \), since \( P(\text{granite} \mid R_1 < R_2 < R_3) > P(\text{basalt} \mid R_1 < R_2 < R_3) \), classify the rock as granite. For \( R_1 < R_3 < R_2 \) and \( R_3 < R_1 < R_2 \), calculate similarly: - For \( R_1 < R_3 < R_2 \), compute probabilities and classify (details follow). - For \( R_3 < R_1 < R_2 \), compute probabilities and classify (details follow).
06

Compute Errors in Classification

To determine the probability of an erroneous classification, we calculate:\[\text{Error} = P(R_1<R_2<R_3 \mid \text{basalt}) \times P(\text{basalt}) + P(R_3<R_1<R_2 \mid \text{granite}) \times P(\text{granite}).\]\( \text{Error} = 0.1 \times 0.75 + 0.15 \times 0.25 = 0.075 + 0.0375 = 0.1125. \)
07

Examine Influence of Changing Prior Probability

For part (d), if \( P(\text{granite}) = p \), showing \( p > 0.6 \) means \( P(\text{granite} \mid \text{order}) > 0.5 \) for \( R_1<R_2<R_3 \) since it's suboptimal otherwise. Solving for all potential outcomes requires setting up the inequality for each possible spectral order.

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Key Concepts

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

Probability Distribution
In the context of the exercise, probability distributions are essential for understanding the likelihood of encountering certain spectral intensity orders in different types of rocks. A probability distribution assigns a probability to each potential outcome, whether it's related to a characteristic of a rock, or the order in which spectral intensity measurements appear.

For granite and basalt rocks, probability distributions help us to understand how likely it is to see the spectral orderings
  • \( R_1 < R_2 < R_3 \)
  • \( R_1 < R_3 < R_2 \)
  • \( R_3 < R_1 < R_2 \)
These distributions are provided in percentages within the context of the exercise.

Understanding these allows us to make informed predictions about the type of rock based on spectral measurement.

Conditional Probability
Conditional probability is key in this exercise because it helps determine the probability of one event occurring given that another event has already occurred. For example, we look at the probability of the rock being granite given that the spectral order is \( R_1 < R_2 < R_3 \).

Using Bayes' Theorem, these probabilities are calculated as follows:
  • \( P( ext{granite} \mid R_1 < R_2 < R_3) \)
  • \( P( ext{basalt} \mid R_1 < R_2 < R_3) \)
In each case, we use known probabilities about the rock types and spectral orders to deduce new probabilities. This approach allows for more reliable predictions and classifications as it considers existing knowledge about the rock's properties.

Bayes' Theorem enhances decision-making by effectively updating initial beliefs with new evidence.
Classification Error
Classification error occurs when the predicted classification of a rock, based on spectral measurements, does not match its true type. Assessing these errors is crucial for understanding the accuracy and reliability of our classification process.

Errors can include:
  • Classifying granite as basalt
  • Classifying basalt as granite
To evaluate such errors, we use previously calculated probabilities:

\( ext{Error} = P(R_1
By quantifying these errors, we learn where the classification system may fall short and can make adjustments to enhance accuracy. This understanding allows us to make more reliable decisions when classifying rocks based on spectral data.
Spectral Analysis
Spectral analysis plays a pivotal role in this exercise as it involves analyzing the intensity of different wavelengths of infrared light reflected from rock surfaces. This information is crucial for distinguishing between granite and basalt.

Typically, the ordering of intensities is indicative of rock type:
  • Granitic: \( R_1 < R_2 < R_3 \)
  • Basaltic: \( R_3 < R_1 < R_2 \)
However, remote measurements from aircraft can vary, leading to different intensity orders. By analyzing these orders, we can make educated guesses about the composition of the surface being scanned.

This type of analysis helps in non-invasive mineral exploration and geological mapping by remotely detecting and classifying surface materials based on their spectral signatures.

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Most popular questions from this chapter

Each of a sample of four home mortgages is classified as fixed rate \((F)\) or variable rate \((V)\). a. What are the 16 outcomes in \(\mathcal{S}\) ? b. Which outcomes are in the event that exactly three of the selected mortgages are fixed rate? c. Which outcomes are in the event that all four mortgages are of the same type? d. Which outcomes are in the event that at most one of the four is a variable- rate mortgage? e. What is the union of the events in parts (c) and (d), and what is the intersection of these two events? f. What are the union and intersection of the two events in parts (b) and (c)?

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An oil exploration company currently has two active projects, one in Asia and the other in Europe. Let \(A\) be the event that the Asian project is successful and \(B\) be the event that the European project is successful. Suppose that \(A\) and \(B\) are independent events with \(P(A)=.4\) and \(P(B)=.7\). a. If the Asian project is not successful, what is the probability that the European project is also not successful? Explain your reasoning. b. What is the probability that at least one of the two projects will be successful? c. Given that at least one of the two projects is successful, what is the probability that only the Asian project is successful?

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