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188 VARGHA ANDRÁSTHOUGHTS ABOUT THE EXPLANATIONOF THE PARTIAL CORRELATION COEFFICIENT(SUMMARY)The partial correlation is a frequently used coefficient for assessing the bivariate correlation of twovariables by eliminating the influence of one or more other variables. The partial correlation is generallyinterpreted as the correlation under the condition that the variables to be eliminated are fixed (notallowed to vary and influencing the dependent variables) that is called in the statistical literature asconditional correlation.The present paper convincingly shows that under the violation of the assumption of multivariatenormality (frequently due to nonlinear relationships among the variables investigated) the usual interpretationof the partial correlation coefficient can be basically incorrect. It may occur such an extremecase that the value of the partial correlation coefficient is highly positive, close to 1, whereas the conditionalcorrelation is a large negative value. To heal this problem the paper suggests to partial outcertain function (in the simplest case the square) of the variables whose effects are to be eliminated ifnonlinear relationships are likely to occur.Keywords: Partial correlation, conditional correlation, smoothed nonlinear regression, ROPstat