O que é Antithetic variates, control variate, stratified sampling?

Antithetic variates pair each draw $Z$ with $-Z$ (each uniform $U$ with $1 - U$) and average $\frac12(f(Z) + f(-Z))$. A control variate is a variable $C$ with known mean, used in $\hat\mu_\beta = \frac1n\sum_i(Y_i - \beta(C_i - \E C))$. Stratified sampling partitions the space of an input into strata of known probability $p_s$ and draws a fixed number $n_s = np_s$ in each.