Tuesday, November 26, 2024

Machine Learning MCQ - Generative vs Discriminative models

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Machine Learning MCQ - Why Naive Bayes classifier is a generative model?

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1. Which is true about generative and discriminative models?

a) Generative models model the joint distribution P(class = C AND sample = x)

b) Perceptron is a generative model

c) Logistic regression is a generative model

d) The naive Bayes classifier is a generative model

 

Answer: (a) Generative models model the joint distribution P(class = C AND sample = x) and (d) The naive Bayes classifier is a generative model

(a) Generative models model the joint distribution

The joint distribution P(X,Y) is the probability distribution that describes how the features X and the labels Y are distributed together. It gives us the probability of observing a particular combination of features X and the associated class label Y simultaneously.

The generative models are those that model the joint distribution because they aim to describe the probabilistic relationship between both the input data (features) and the output label (class), together. In other words, generative models try to understand how the data is generated in the context of both the features and the labels.

 

(d) Naïve Bayes is generative model

Naive Bayes is generative because it models how the data (features and labels) are generated. Specifically, it models the joint probability P(X,Y) by assuming a probabilistic process where the features are generated given the class label. It then uses Bayes' theorem to compute the posterior probability of the class, making it a generative model that focuses on how the data comes together. This contrasts with discriminative models, which directly model the decision boundary without modeling how the data is generated.

Suppose that you are using Naïve Bayes to classify emails as ‘spam’ or ‘not spam’. In this classification, the Naive Bayes model has "generated" a probabilistic model of the features (words) conditioned on the class (spam or not spam). That is it calculates the likelihood of observing words given the class [P(word|spam) and P(word|no spam)]. This is why it’s considered generative.

 

Logistic regression is a discriminative model which focuses on directly modeling the decision boundary of classes based on estimating the conditional probability which is P(Y|X).

Perceptron is a discriminative model.

 

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Related links:

Why naive bayes is a generative classifier?

Generative vs discriminative machine learning algorithm

Why perceptron is a discriminative classifier?

Why logistic regression is a discriminative classifier?

generative model uses joint probability distribution whereas discriminative model uses the conditional probability distribution

Machine learning solved mcq, machine learning solved mcq 

 

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