DSE Data Science 3

Question 1

What distinguishes a random forest from a single decision tree?

Accepted Answer

It aggregates predictions from multiple trees trained on random subsets

Answer

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

Question 2

What is the Gini impurity used for in decision trees?

Accepted Answer

Evaluating how balanced classes are at a node when splitting

Answer

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

Question 3

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

Accepted Answer

ReLU

Answer

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

Question 4

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

Accepted Answer

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

Answer

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

Question 5

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

Accepted Answer

Information from outside the training set influencing model training

Answer

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

DSE - Data Science Practice Test