Machine Learning Unit I Concepts
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Questions and Answers

What is the primary purpose of machine learning algorithms?

  • To predict outcomes and classify information (correct)
  • To perform manual tasks with precision
  • To memorize data without analysis
  • To replace human intelligence entirely
  • Which of the following is NOT a type of machine learning?

  • Reinforced Learning (correct)
  • Reinforcement Learning
  • Unsupervised Machine Learning
  • Supervised Machine Learning
  • How does supervised machine learning operate?

  • It requires human intervention for every decision.
  • It learns without any guidance or feedback.
  • It learns from labeled data with known outcomes. (correct)
  • It mimics human intuition to make predictions.
  • Which of these applications would best illustrate unsupervised learning?

    <p>Clustering customers based on purchasing behavior</p> Signup and view all the answers

    What is the bias-variance trade-off in machine learning?

    <p>A balance between model complexity and error rates</p> Signup and view all the answers

    In what year was the term 'machine learning' first used, and by whom?

    <p>1959 by Arthur Samuel</p> Signup and view all the answers

    What role does the confusion matrix play in machine learning?

    <p>It visualizes the performance of a classification algorithm.</p> Signup and view all the answers

    Which of the following scenarios best exemplifies reinforcement learning?

    <p>A robot learning to navigate a maze by trying various paths and receiving rewards.</p> Signup and view all the answers

    What is the definition of joint probability?

    <p>The probability of two independent events occurring simultaneously.</p> Signup and view all the answers

    How is the joint probability of two independent events A and B calculated?

    <p>P(A) * P(B)</p> Signup and view all the answers

    Which of the following pairs of events is considered independent?

    <p>Flipping a coin twice.</p> Signup and view all the answers

    If P(Red ∩ Dog) = 0.05, what does this represent?

    <p>The joint probability of liking red and owning a dog.</p> Signup and view all the answers

    Calculate P(H1 ∩ H2), the probability of getting heads on both flips.

    <p>$1/4$</p> Signup and view all the answers

    For dependent events, how is joint probability represented?

    <p>P(A) * P(B|A)</p> Signup and view all the answers

    What is P(B|A) in the context of joint probability for dependent events?

    <p>The probability of event B occurring given that event A has happened.</p> Signup and view all the answers

    Given P(smoker) = 0.2 and P(obese) = 0.3, what is the joint probability if the events are independent?

    <p>0.06</p> Signup and view all the answers

    What is the primary purpose of Linear Discriminant Analysis (LDA) in machine learning?

    <p>To maximize distance and minimize variance for better class separation.</p> Signup and view all the answers

    What does False Positive (FP) signify in classification metrics?

    <p>The model incorrectly predicted a positive instance.</p> Signup and view all the answers

    Which two criteria does LDA use to create a new axis?

    <p>Maximizing distance between class means and minimizing within class variance.</p> Signup and view all the answers

    In the context of the confusion matrix, what is True Negative (TN)?

    <p>The actual negative instances correctly predicted.</p> Signup and view all the answers

    In what scenario does LDA especially excel compared to Logistic Regression?

    <p>In cases of multiple classification problems with well-separated classes.</p> Signup and view all the answers

    When calculating the accuracy of a model, what is the formula used?

    <p>(TP + TN) / Total Predictions</p> Signup and view all the answers

    What type of data pre-processing can LDA perform?

    <p>It can reduce the number of features similar to PCA.</p> Signup and view all the answers

    Why is LDA considered useful in face detection algorithms?

    <p>It extracts useful data from varying facial characteristics.</p> Signup and view all the answers

    For the Setosa class, what are the True Positive (TP) and False Negative (FN) values?

    <p>TP = 0, FN = 0</p> Signup and view all the answers

    What is indicated by a high value of True Positives (TP)?

    <p>The model is accurately identifying instances of the positive class.</p> Signup and view all the answers

    How does LDA achieve improved class separability?

    <p>By generating a straight line that completely separates classes.</p> Signup and view all the answers

    Which of the following is NOT a benefit of using LDA?

    <p>It can lead to overfitting in high-dimensional data.</p> Signup and view all the answers

    Given the model classified 100 tumors and the TN count is 90, what can be concluded?

    <p>The model is effectively predicting negative instances.</p> Signup and view all the answers

    What is a critical limitation of accuracy as a metric in model evaluation?

    <p>It may be misleading for imbalanced datasets.</p> Signup and view all the answers

    What dimensionality reduction is achieved by applying LDA to a 2-D dataset?

    <p>Reduction to 1-D space.</p> Signup and view all the answers

    For the Versicolor class, what are the False Positive (FP) and True Negative (TN) values?

    <p>FP = 0, TN = 27</p> Signup and view all the answers

    What condition causes Linear Discriminant Analysis (LDA) to fail?

    <p>When the mean of the distributions is shared</p> Signup and view all the answers

    In which application is Linear Discriminant Analysis primarily used?

    <p>Classifying diseases in medical fields</p> Signup and view all the answers

    Which analysis technique reduces the dimensionality while retaining maximum information from the dataset?

    <p>Principal Component Analysis</p> Signup and view all the answers

    What is the primary function of LDA in face recognition?

    <p>To minimize the number of features before classification</p> Signup and view all the answers

    Which matrix is NOT involved in the calculations of LDA?

    <p>Correlation matrix</p> Signup and view all the answers

    What does LDA accomplish in the context of supervised classification?

    <p>Classes are projected onto a lower-dimensional space</p> Signup and view all the answers

    What is the output of the new features obtained from Principal Component Analysis called?

    <p>Principal Components</p> Signup and view all the answers

    When dealing with linear separability, which approach is recommended when LDA encounters shared means?

    <p>Switch to non-linear Discriminant Analysis</p> Signup and view all the answers

    Study Notes

    Introduction to Machine Learning

    • Machine learning enables machines to learn from experiences and past data, similar to human learning.
    • Arthur Samuel coined the term "machine learning" in 1959; it is a subfield of artificial intelligence (AI).
    • Algorithms trained on datasets create self-learning models for predicting outcomes and classifying data without human intervention.
    • Machine learning applications include recommendation engines, speech recognition, fraud detection, and self-driving vehicle features.

    Types of Machine Learning

    • Machine learning is categorized into three main types:
      • Supervised Learning
      • Unsupervised Learning
      • Reinforcement Learning

    Supervised Machine Learning

    • Analogous to a teacher guiding students, it uses labeled data for training.
    • Key performance metrics include:
      • True Positive (TP): Correctly predicted positives.
      • False Positive (FP): Incorrectly predicted positives (Type 1 Error).
      • False Negative (FN): Incorrectly predicted negatives (Type 2 Error).
      • True Negative (TN): Correctly predicted negatives.
    • Confusion Matrix: A table to visualize performance across classes for classification tasks.

    Accuracy Metrics

    • Accuracy = (TP + TN) / Total Predictions.
    • High accuracy does not suffice for imbalanced datasets; alternative metrics may be needed.

    Probability in Machine Learning

    • Probability denotes the likelihood of events; denoted as P(X).
    • Joint Probability: P(A ∩ B) = P(A) * P(B) for independent events.
    • Joint probability for dependent events: P(A ∩ B) = P(A) * P(B|A).

    Dimensionality Reduction Techniques

    • Linear Discriminant Analysis (LDA):

      • Transforms multiple dimensions into a lower-dimensional space to maximize class separability.
      • Prioritizes maximizing the distance between class means and minimizing variance within classes.
      • Useful for face detection and medical classification.
    • Principal Component Analysis (PCA):

      • Maps higher-dimensional data to a lower-dimensional space while preserving variance.
      • Aims to retain maximum information from the original dataset with minimal correlation among new components.

    Applications of LDA

    • Widely used in face recognition to reduce the number of features before classification.
    • Assists in medical diagnosis classification based on patient data to inform treatment plans.

    Summary of Analysis Steps for LDA

    • Step 1: Calculate means for each class.
    • Step 2: Compute covariance matrices for classes.
    • Step 3: Determine within-class scatter matrix.
    • Step 4: Calculate between-class scatter matrix.

    Remember: LDA is effective for supervised classification tasks, particularly when classes are well-separated but may fail with overlapping distributions.

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    Description

    This quiz covers the foundational concepts of machine learning, including types of machine learning, bias-variance tradeoff, and evaluation metrics such as confusion matrix and accuracy. It also delves into dimensionality reduction techniques like PCA and LDA, critical for processing data effectively.

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