ML/DL Concept Questions (Take‑home)
Provide concise, correct answers to each prompt.
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PCA
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What do the eigenvectors of the covariance matrix represent?
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How do they relate to principal components and explained variance?
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Decision Trees
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Define Gini impurity.
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Show how to compute it for a node.
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Explain how it is used to choose splits.
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Reinforcement Learning
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Write the Bellman optimality equation (for V* or Q*).
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Explain its role in policy evaluation and improvement.
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Regularization (Dropout)
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What is dropout?
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How does it behave at training vs. inference time?
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Why does it act as a regularizer?
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Training Stability
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What is gradient clipping and when is it useful?
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How do residual connections in ResNets help mitigate vanishing gradients?
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Optimization Landscape
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Why are deep learning objectives typically non‑convex?
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What are the practical implications for optimization (e.g., local minima vs. saddle points)?
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Transformers
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Describe scaled dot‑product attention.
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Explain why the dot products are scaled by 1/sqrt(d_k).