# Tutor profile: Andrew F.

## Questions

### Subject: Statistics

Why is cross-validation used in finding the uncertainty of estimates?

Cross-validation reduces the loss of training data from data splitting in order to find an unbiased measure of uncertainty (usually, mean squared error). CV is used to limit overfitting, and keep measures of uncertainty from being overly optimistic.

### Subject: Economics

What is a visual way to understand the Gini coefficient?

The Lorenz curve graphs the cumulative population (from lowest to highest income) on the horizontal axis against the cumulative share of income on the vertical axis. The Gini coefficient represents the fraction of the area below the 45 degree line that is above the Lorenz curve.

### Subject: R Programming

Why are vector operations preferred over iteration in R?

In short, vectorized functions and operations run much faster than iterated ones do in R. Especially with operations that are done many times or repeatedly, vectorizing will reduce runtime significantly over iteration.

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