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. 2017 Dec 11;17:246. doi: 10.1186/s12909-017-1070-5

Fig. 1.

Fig. 1

a Scattergram of X1 and X2. 20% of 1000 applicants are selected by the sum of X1 and X2; the circular cloud representing all applicants is divided by a diagonal line that separates the top right area from the bottom left area. b This generates a negative correlation between X1 and X2 in the incumbents rx1x2i=0.71. Residuals of X1 after the linear effect of X2 is removed. They are expressed as deviations from the regression line: The residuum of X1 when the influence of X2 is removed is the observed X1 value minus the expected value of the regression X1 on X2