Start with Gaussians
Generate independent standard normal variables, which are easy to simulate.
Creating complex distributions from simple random samples
Monte Carlo methods use repeated random sampling to produce numerical answers. A simple random variable can be transformed into one with a very different distribution.
The essential idea: sample something easy, transform it, and let the empirical pattern reveal the target distribution.
Generate independent standard normal variables, which are easy to simulate.
The sum of their squares follows a chi-squared distribution with k degrees of freedom.
Choose the degrees of freedom and the sample count. The empirical histogram approaches the theoretical density as sampling increases.
Monte Carlo can approximate a complicated distribution by manipulating samples from simpler distributions.