Data Science Flashcards

What distinguishes a random forest from a single decision tree?

Answer: It aggregates predictions from multiple trees trained on random subsets

Random forests build an ensemble of trees using bootstrap sampling and feature randomness to reduce variance.

What is the Gini impurity used for in decision trees?

Answer: Evaluating how balanced classes are at a node when splitting

Gini impurity measures the probability of misclassifying a randomly chosen element if labeled by its class distribution.

Which activation function is most commonly used in hidden layers of deep neural networks today?

Answer: ReLU

ReLU (Rectified Linear Unit) avoids the vanishing gradient problem and is computationally efficient.

In natural language processing, what is TF-IDF designed to measure?

Answer: The importance of a word to a document relative to a corpus

TF-IDF weights a term by how often it appears in a document scaled by how rare it is across the corpus.

What is meant by data leakage in a machine learning pipeline?

Answer: Information from outside the training set influencing model training

Data leakage causes artificially inflated performance metrics because the model learns information it shouldn't have access to.

Which statistical test is most appropriate for comparing means across three or more independent groups?

Answer: One-way ANOVA

One-way ANOVA tests whether at least one group mean differs significantly from the others.

What does ROC-AUC measure in a binary classification model?

Answer: The model's ability to rank positive instances higher than negatives across all thresholds

AUC represents the probability that a randomly chosen positive example is ranked higher than a randomly chosen negative one.