11 -Introduction to Topic Modeling
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Questions and Answers

What is the main purpose of factor analysis of the document-term matrix?

To determine the similarity of words based on the documents they cooccur in and the similarity of documents based on the words they contain.

What does Singular Value Decomposition (SVD) help in achieving in the context of document-term matrix?

It helps in obtaining the best (least-squares) approximation by truncating the matrix to topics.

How can the complexity of SVD on a matrix be reduced?

By approximating it using Monte-Carlo sampling if only a certain number of components are needed.

What is the key idea behind the probabilistic topic modeling?

<p>Every document and every word is considered as a mixture of topics.</p> Signup and view all the answers

What does a probabilistic topic model entail for every document and word?

<p>For every document: a topic distribution, and for every word: a word distribution for every topic.</p> Signup and view all the answers

Does SVD yield probabilities directly? Explain.

<p>No, SVD does not yield probabilities directly, but the factors obtained can contain negative values.</p> Signup and view all the answers

What is the main goal of topic modeling in relation to a text corpus?

<p>Find the latent structure that resembles topics and best summarizes the collection.</p> Signup and view all the answers

How does Latent Semantic Indexing (LSI) or Latent Semantic Analysis (LSA) help in information retrieval?

<p>It helps address challenges like synonymy and polysemy in information retrieval.</p> Signup and view all the answers

What distinguishes topic modeling from clustering in terms of emphasis?

<p>In clustering, the emphasis is on data points/documents, while in topic modeling, the emphasis is on the topics/clusters themselves.</p> Signup and view all the answers

Why is exact search problematic in information retrieval when dealing with synonymy and polysemy?

<p>Exact search will not find synonyms and will include polynyms and homonyms.</p> Signup and view all the answers

What is the purpose of identifying 'factors' in Latent Semantic Indexing for document representation?

<p>Factors provide a lower-dimensional representation of the document.</p> Signup and view all the answers

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