CSDS 391 Intro to AI: Learning from Examples
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Questions and Answers

What is the primary focus of the course CSDS 391?

  • Operating Systems
  • Machine Learning Algorithms
  • Intro to AI (correct)
  • Data Structures
  • Learning from examples is a fundamental aspect of AI.

    True (A)

    What type of data is focused on when predicting credit risk in AI?

    credit risk data

    In AI, learning from examples typically involves classifying __________ data.

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

    Match the following AI concepts with their descriptions:

    <p>Learning from Examples = Utilizing data to improve predictions Classifying Uncertain Data = Sorting data into categories despite uncertainty Predicting Credit Risk = Assessing the likelihood of default on loans AI = Simulating human intelligence in machines</p> Signup and view all the answers

    What is a potential advantage of using distance metrics like Euclidean distance in clustering applications?

    <p>It does not require an explicit model. (D)</p> Signup and view all the answers

    Euclidean distance is an effective method for handling high-dimensional data classification.

    <p>True (A)</p> Signup and view all the answers

    What is the classification error percentage for the 7-nearest neighbor approach on handwritten digits using leave-one-out?

    <p>4.85%</p> Signup and view all the answers

    The distance metric formula $d(x, y) = \sum (x_i − y_i)^2$ is used to calculate __________.

    <p>Euclidean distance</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>K-means = A clustering algorithm that partitions data into k clusters. Leave-one-out = A method for validating the performance of a model. Euclidean distance = A distance metric calculated by the square root of summing squared differences. 7-nearest neighbor = A classification approach that uses the closest 7 examples for decision-making.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of clustering techniques?

    <p>Clustering requires prior knowledge of class labels. (A)</p> Signup and view all the answers

    A disadvantage of using Euclidean distance is that it may not perform well in all cases.

    <p>True (A)</p> Signup and view all the answers

    Why is it said that using distance metrics requires no 'brain' on the part of the designer?

    <p>Because it automates the classification process based on data features.</p> Signup and view all the answers

    Which of the following describes the k-nearest neighbors algorithm?

    <p>It looks at k-nearest neighbors and chooses the most frequent class. (A)</p> Signup and view all the answers

    The Euclidean distance metric considers how many pixels overlap in image data.

    <p>True (A)</p> Signup and view all the answers

    What kind of distance metric could be defined to improve classification in k-nearest neighbors?

    <p>A distance metric that is insensitive to small deviations in position, scale, or rotation.</p> Signup and view all the answers

    The k-nearest neighbors algorithm is typically evaluated based on its error rate on __________ data.

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

    What potential issue arises when finding neighbors in the k-nearest neighbors algorithm?

    <p>It can become computationally expensive. (D)</p> Signup and view all the answers

    Match the following clustering techniques with their characteristics:

    <p>K-means = Partitions data into k clusters based on distance to the centroid. Hierarchical clustering = Creates a tree-like structure of clusters. DBSCAN = Clusters based on density of data points. Mean-shift = Finds modes of the data distribution.</p> Signup and view all the answers

    Small deviations in image position, scale, or rotation can significantly impact Euclidean distance calculations.

    <p>True (A)</p> Signup and view all the answers

    What is the main objective of using distance metrics in clustering algorithms?

    <p>To accurately measure the similarity or dissimilarity between data points.</p> Signup and view all the answers

    What is the primary criterion for the optimal decision boundary in classification?

    <p>Minimizing the misclassification error (D)</p> Signup and view all the answers

    Euclidean distance is commonly used to measure the similarity between points in nearest neighbor classification.

    <p>True (A)</p> Signup and view all the answers

    What is the assumption made about class probability in the context of the optimal decision boundary?

    <p>p(C3 |x) = p(C2 |x)</p> Signup and view all the answers

    In classification, points that are nearby are likely to belong to the same __________.

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

    Match the following distance metrics with their applications:

    <p>Euclidean distance = Measuring straight-line distance in multi-dimensional space Manhattan distance = Calculating distance along axes at right angles Minkowski distance = Generalization of Euclidean and Manhattan distances Cosine similarity = Determining the angle between two vectors</p> Signup and view all the answers

    What does 'p(x|C2)' refer to in a classification context?

    <p>Probability of feature x given class C2 (D)</p> Signup and view all the answers

    A misclassification error occurs when a classified point is correctly categorized into its true class.

    <p>False (B)</p> Signup and view all the answers

    Name one clustering technique other than K-means.

    <p>Hierarchical clustering</p> Signup and view all the answers

    Flashcards

    Credit risk data

    Data used to predict if someone will default on a loan.

    Predicting credit risk

    Using data to forecast if someone will default on a loan.

    Learning from examples (in AI)

    Using past data to build models that predict future events.

    Classifying uncertain data

    Categorizing data with uncertain values for predictions.

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    AI for Credit Risk

    Using AI to make decisions about loan risks based on data

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    k-Nearest Neighbors

    A classification algorithm that predicts the class of a data point based on the majority class of its k nearest neighbors in the feature space.

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    Euclidean Distance

    A measure of distance between two points in a multi-dimensional space, calculated as the square root of the sum of squared differences between corresponding coordinates.

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    Nearest Neighbor Classifier

    A type of classifier that directly predicts the class of a data point based on the class label of its nearest neighbor in the feature space.

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    Template Matching

    A technique used in computer vision to find instances of a specific pattern (template) within an image by calculating the similarity between the template and different regions of the image.

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    Distance Metric in AI

    Any function that measures the distance or dissimilarity between two objects or data points in a feature space. This can be used to implement algorithms like nearest neighbor classification.

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    Sensitivity to Deviations

    The ability of a distance metric to be influenced by small changes or variations (deviations) in the data, such as shifts in position or scale.

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    Data Sensitivity Challenge

    The issue of designing a distance metric that is insensitive to minor changes (deviations) in the data, such as shifts in position, scale, or rotation, but sensitive to meaningful differences.

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    Classifiers in Machine Learning

    Algorithms that learn a mapping from inputs to outputs, specifically for categorizing data points into predefined classes.

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    k-NN algorithm

    A classification algorithm where a new data point is assigned to the class of its k nearest neighbors in a training dataset.

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    Leave-one-out error

    A way to estimate the generalization error of a model by training the model on all data except one example and then testing the model on the excluded example. This process is repeated for each example, and the error rate is averaged over all examples.

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    What makes k-NN easy to implement?

    The k-NN algorithm is straightforward to implement because it doesn’t require training a specific model. Instead, it simply relies on calculating distances and finding the nearest neighbors.

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    How does k-NN handle complex classes?

    The k-NN algorithm can handle complex class boundaries by considering the distribution of neighboring data points.

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    Advantages of k-NN

    The k-NN algorithm has several advantages, including its simplicity, ability to handle complex classes, and its ability to improve with more data points. Additionally, it doesn’t require a specific model to be built.

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    What does the error bound formula tell us about k-NN?

    The error bound formula for the k-NN algorithm shows that the error rate can be reduced by increasing the number of training examples (N) and by choosing an appropriate value for k, the number of neighbors.

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    How does the USPS dataset exemplify k-NN?

    The USPS dataset, consisting of images of handwritten digits, can be used to demonstrate the effectiveness of k-NN. The algorithm can classify a new digit image by comparing it to the nearest known digit images.

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    Optimal Decision Boundary

    The boundary that minimizes misclassification error by dividing data points into their most likely classes. It's determined where the probabilities of belonging to two classes are equal.

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    Probability Condition for Optimal Boundary

    The optimal decision boundary occurs when the probability of a data point belonging to class C3 equals the probability of it belonging to class C2.

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    Nearest Neighbor Classification

    A method that classifies a new data point by assigning it to the class of its nearest known data point.

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    How does Euclidean distance help with classification?

    It allows us to determine which known data point is closest to a new data point, suggesting that the new point is likely to belong to the same class as its closest neighbor.

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    Assumption of Nearest Neighbor Classification

    Assumes that points close together in the data space are likely to belong to the same class.

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    What if a new data point is equidistant to two known data points from different classes?

    There are various tie-breaking techniques, such as choosing the class with the most neighbors within a small radius around the unknown point.

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    When does Nearest Neighbor work well?

    It works well when data points within the same class tend to cluster together and are well separated from points belonging to other classes.

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    Study Notes

    CSDS 391 Intro to AI: Learning from Examples

    • Classifying Uncertain Data:
      • The example concerns credit risk assessment
      • Learning the best classification from data involves estimating the strength of a credit risk.
      • Flexibility in decision criteria is useful, for example taking higher risks during good times or more carefully examining higher-risk applicants.

    Credit Risk Prediction

    • Predicting credit risk involves analyzing factors like years at a current job, missed payments and whether or not an individual defaulted.

    Mushroom Classification

    • Mushroom classification uses a guide to assess edibility based on criteria. -Certainty about a mushroom's safety can't be perfectly predicted by the criteria alone.
      • The data for edible and poisonous mushrooms is displayed.

    Bayesian Classification

    • Class conditional probability is recalled using mathematical formulas.
      • The likelihood of data (x) given a class (Ck) is to be determined.

    Defining a Probabilistic Classification model

    • A probabilistic classification model can define a credit risk problem in terms of classes (e.g., defaulted or not defaulted) and data (e.g., years at a job, missed payments).
      • Prior probabilities (e.g., probability of default), and likelihoods (e.g. probability of features given a class) need to be determined.

    Defining a Probabilistic Model by Counting

    • Prior probabilities are determined by counting the occurrence of each class in the data.

      • Likewise likelihood is determined by counting the occurrences of certain feature values given a class.
    • Maximum likelihood estimate (MLE) explains the method

    Determining Likelihood

    • A simple approach involves counting the instances matching specific feature combinations and class labels in the data.

    Being (Proper) Bayesians: Coin Flipping

    • Bernoulli trials are used to examine how probability is determined when each trial's outcome is either heads (1) with probability θ or tails (0) with probability 1-θ.

    • The Binomial distribution describes probability of getting a specific number of heads (y) in a series of trials (n).

    Applying Bayes' Rule

    • Bayes' rule is used to update knowledge after new observations are made

      • Likelihood(y|θ,n) x Prior(θ|n) = Posterior(θ|y,n)
    • A reasonable uniform prior assumption states that you have no prior knowledge about the parameter θ.

      • The posterior is proportional to the likelihood in this case

    An Example with Distributions: Coin Flipping

    • The likelihood for different possible values of θ is viewed graphically

    Bayesian Inference

    • Bayesian inference addresses situations with continuous variables.
    • Likelihood (y| θ, n) x prior θ = posterior ( θ | y,n)

    Updating Knowledge

    • After observing new information, a posterior distribution can be determined

    Evaluating the Posterior

    • Before observing any trials, the prior probability distribution of θ is uniform

    Coin Tossing

    • Examples demonstrate how knowledge about θ is updated with different numbers of heads and tails in coin-tossing trials

    Evaluating the Normalizing Constant

    • The normalizing constant is needed to obtain the proper probability density functions

    More Coin Tossing

    • An example demonstrates the scenario with more coin trials, like 50 trials.

    Estimates for Parameter Values

    • Two approaches are noted, Maximum likelihood estimate (MLE) and Maximum a posteriori (MAP) estimate.
      • MLE involves taking the derivative of the likelihood and setting it to zero to find the parameter that maximizes the likelihood. The prior is not taken into account.

      • MAP on the other hand accounts for the prior by finding an estimate from the equation of posterior.

    The Ratio Estimate

    • Intuitive approach to estimate the parameter for values.
      • The estimate for the current example is the proportion of heads from the number of total trials.

    The Maximum A Posteriori (MAP) Estimate

    • Involves finding the value of the parameter that maximizes the posterior distribution
      • Same as ratio estimate in the current example.

    The Ratio Estimate cont'd

    • The MAP and ratio estimation are examined with one trial and more trials

    Expected Value Estimate

    • This is calculated as the mean of the probability density function.
      • The average value of the parameter over the whole distribution is calculated.

    On To The Mushrooms!

    • Mushroom data is presented.
      • The data for edible and poisonous mushrooms based on features like cap shape, cap surface, odor, stalk shape and population is displayed.

    The Scaling Problem

    • The issue of large data sets and the huge number of parameters in the likelihood calculation is highlighted.

    Mushroom Attributes

    • Attributes like cap shape and cap surface, along with values like color and odor of mushrooms, are presented
      • The amount of data and the associated values for each feature are showcased

    Simplifying With "Naïve" Bayes

    • The Naïve Bayes approach to finding the probability of a class given an example (x) is examined.
      • An assumption is made that the features are independent. Given this assumption the probability is easier to calculate since the likelihood of multiple features can be calculated by multiplying the likelihood for each of the individual features.

    Inference With Naïve Bayes

    • Inference is made by making assumptions that features are independent of each other to calculate conditional probability

    Implementation Issues:

    • Log probabilities are used to address computational problems from calculating products of probability values
      • In Naïve Bayes calculation, instead of multiplying probabilities directly, log transformations of probabilities are calculated, and then added.

    Converting Back To Probabilities

    • Log transformation is used to address computation issues
      • The log probabilities are shifted to zero, for normalized calculation

    Text Classification With The Bag of Words Model

    • The bag-of-words model
      • Documents are represented as vectors, where each element represents the count of a specific word

      • The differences in word frequencies are apparent and can be used to classify different document types.

      • Naïve Bayes is applied to classify documents.

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    CSDS 391 Intro to AI PDF

    Description

    This quiz covers concepts from CSDS 391, focusing on AI techniques for classifying uncertain data. Topics include credit risk assessment, mushroom classification, and Bayesian classification methods. Additionally, it explores the importance of flexibility in decision criteria when making predictions.

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