MS-DS Master of Data science Master of Data Science Machine Learning 1

Question 1

Which cross-validation technique is most appropriate when the dataset is small and every data point must be used for both training and testing?

Accepted Answer

Leave-one-out cross-validation

Answer

Leave-one-out cross-validation (LOOCV) trains the model on all data points except one, repeating this for every data point. This maximizes training data usage, making it ideal for small datasets where a fixed holdout split would waste too much data.

Question 2

In gradient boosting, each successive tree is trained to predict what?

Accepted Answer

The residual errors of the previous ensemble

Answer

Gradient boosting builds trees sequentially where each new tree fits the residual errors (pseudo-residuals) left by the previous ensemble. This additive correction process allows the model to progressively reduce error.

Question 3

What is the primary purpose of the kernel trick in Support Vector Machines?

Accepted Answer

To map data into a higher-dimensional space without computing the transformation explicitly

Answer

The kernel trick allows SVMs to operate in a high-dimensional feature space by computing dot products in that space implicitly, using a kernel function. This makes it computationally feasible to find non-linear decision boundaries without explicitly computing the high-dimensional mapping.

Question 4

A model has high training accuracy but significantly lower test accuracy. This pattern is most indicative of which problem?

Accepted Answer

Overfitting

Answer

A large gap between training accuracy and test accuracy indicates overfitting — the model has learned the training data's noise and specific patterns rather than generalizable relationships, causing it to perform poorly on unseen data.

Question 5

In Principal Component Analysis (PCA), the principal components are defined as:

Accepted Answer

The eigenvectors of the feature covariance matrix, ordered by eigenvalue magnitude

Answer

PCA computes the covariance matrix of the features and finds its eigenvectors. Each eigenvector (principal component) points in a direction of variance in the data, and the corresponding eigenvalue measures the amount of variance explained. Components are ordered from highest to lowest eigenvalue.

MS-DS Master of Data science Practice Test

MS-DS Master of Data science Practice Test

MS-DS Master of Data science Master of Data Science Machine Learning 1