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Machine Learning Fundamentals: Model Selection and Overfitting
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Machine Learning Fundamentals: Model Selection and Overfitting

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Questions and Answers

What is the purpose of model selection in machine learning?

  • To find the best model/hypothesis and optimize hyper parameters (correct)
  • To compute the Euclidean distance between data points and clusters centroids
  • To divide the dataset into training, validation, and testing sets
  • To refine the clusters centroids positions
  • Why does both validation error and testing error increase as the validation set increases?

  • Due to the lack of sufficient data in the validation set
  • Due to the increase in the training error (correct)
  • Due to the decrease in the training error
  • Due to the decrease in the size of the training set
  • In machine learning, what distinguishes supervised learning from unsupervised learning?

  • Supervised learning uses dimensionality reduction while unsupervised learning does not
  • Supervised learning involves clustering while unsupervised learning does not
  • Supervised learning has more hyperparameters to optimize compared to unsupervised learning
  • Supervised learning includes classifying data based on labels while unsupervised learning does not (correct)
  • What is the main process involved in K-means clustering?

    <p>Selecting clusters centroids randomly</p> Signup and view all the answers

    What is the primary goal of unsupervised tasks in machine learning?

    <p>To group a set of objects into classes of similar objects</p> Signup and view all the answers

    Why are flat and hierarchical algorithms typically used in clustering?

    <p>To group a set of objects into classes of similar objects</p> Signup and view all the answers

    What is the purpose of re-assigning the clusters centroids positions in K-means clustering?

    <p>To update the cluster assignments of the data points</p> Signup and view all the answers

    What is the mathematical formula used to re-assign new centroids to new positions in K-means clustering?

    <p>μ(c) = ∑|c| x / |c|</p> Signup and view all the answers

    What is the key factor determining the termination conditions in K-means clustering?

    <p>Change in the positions of centroids</p> Signup and view all the answers

    How does K-means convergence relate to the Expectation Maximization (EM) algorithm?

    <p>K-means is a part of the EM algorithm</p> Signup and view all the answers

    What effect does an increase in the number of members in a cluster have on recomputation during K-means clustering?

    <p>It increases the speed of convergence</p> Signup and view all the answers

    What does monotonic decrease in each Gk indicate during recomputation in K-means clustering?

    <p>Decreasing sum of squared distances</p> Signup and view all the answers

    What does Σ(di - a)² reaching minimum imply during recomputation in K-means clustering?

    <p>Convergence to a local minimum</p> Signup and view all the answers

    What is the primary difference between validation error and testing error in machine learning?

    <p>Validation error estimates performance on unseen data, while testing error measures performance on training data</p> Signup and view all the answers

    Why does both validation error and testing error increase as the validation set increases?

    <p>Due to overfitting of complex models on larger validation sets</p> Signup and view all the answers

    What distinguishes supervised learning from unsupervised learning in machine learning?

    <p>In supervised learning, labeled data is available; whereas, in unsupervised learning, only unlabeled data is available.</p> Signup and view all the answers

    Study Notes

    Model Selection

    • The purpose of model selection in machine learning is to choose the best model for a given problem.

    Clustering

    • K-means clustering is a type of unsupervised learning algorithm.
    • The main process involved in K-means clustering is:
      • Initialize centroids randomly
      • Assign data points to the nearest centroid
      • Re-assign centroids to the mean of their assigned data points
      • Repeat until convergence

    Unsupervised Learning

    • The primary goal of unsupervised tasks in machine learning is to identify patterns or structure in the data.

    Supervised vs Unsupervised Learning

    • Supervised learning involves training a model on labeled data to make predictions on new data.
    • Unsupervised learning involves training a model on unlabeled data to discover patterns or structure.

    Clustering Algorithms

    • Flat and hierarchical algorithms are typically used in clustering because they can handle large datasets and identify complex relationships.

    K-means Clustering

    • The purpose of re-assigning the clusters' centroids positions in K-means clustering is to minimize the sum of squared distances between data points and their assigned centroids.
    • The mathematical formula used to re-assign new centroids to new positions in K-means clustering is the mean of all data points assigned to each centroid.
    • The key factor determining the termination conditions in K-means clustering is the convergence of the centroids.
    • K-means clustering is related to the Expectation Maximization (EM) algorithm because both algorithms involve iterative refinement of parameters to maximize the likelihood of the data.

    K-means Convergence

    • An increase in the number of members in a cluster slows down recomputation during K-means clustering.
    • A monotonic decrease in each Gk during recomputation indicates convergence.
    • Σ(di - a)² reaching minimum implies that the centroids have converged.

    Model Evaluation

    • Validation error and testing error increase as the validation set increases because the model is overfitting to the validation set.
    • The primary difference between validation error and testing error is that validation error is used to tune hyperparameters, while testing error is used to evaluate the model's performance on unseen data.

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    Description

    This quiz covers the fundamental concepts of machine learning, including the machine learning process, unseen data, training set, ML algorithm, ML model (hypothesis), prediction process, overfitting, underfitting, and model selection. It also delves into the significance of model selection in finding the best model or hypothesis and optimizing hyperparameters.

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