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(some links; expanded example a bit) 
m (Disambiguated: correlation coefficient → Pearson productmoment correlation coefficient) 

:<math>\rho_{m,t}=\textrm{Corr}\left(m,t\right); \, </math>
is the [[Pearson productmoment correlation coefficientcorrelation coefficient]] of ''m'' and ''t''. The greater the value of <math>\vert\rho_{m,t}\vert</math>, the greater the [[variance reduction]] achieved.
In the case that <math>\textrm{Cov}\left(m,t\right)</math>, <math>\textrm{Var}\left(t\right)</math>, and/or <math>\rho_{m,t}\;</math> are unknown, they can be estimated across the Monte Carlo replicates. This is equivalent to solving a certain [[least squares]] system; therefore this technique is also known as '''regression sampling'''.
