MS-DS Master of Data science Study Guide 2026

A/B testing is a controlled experiment where two variants are compared to measure which one produces a better outcome on a specific metric.

The correlation coefficient, Cor(X, Y), measures the strength and direction of the linear relationship between two random variables X and Y. A value of 0 indicates that there is no linear association between the variables. It's important to note that a correlation of 0 does not necessarily imply independence, as non-linear relationships might still exist.

The '3 V's' (Volume, Velocity, Variety) are commonly associated with Big Data, but 'Veracity' is a fourth crucial dimension. Veracity refers to the trustworthiness, accuracy, and quality of the data, addressing issues like bias, noise, and abnormalities that can significantly impact analysis and decision-making.

The inverse of the Fisher information provides the asymptotic variance of the MLE, forming the basis of the Cramér-Rao lower bound.

For a Chi-squared distribution, the degrees of freedom (often denoted as 'k') define its shape and properties. The mean of a Chi-squared distribution is equal to its degrees of freedom (k), and its variance is equal to twice its degrees of freedom (2k). Therefore, the degrees of freedom are directly related to, and half of, the variance.

PCA identifies principal components as orthogonal directions of maximum variance, enabling dimensionality reduction while preserving the most information.