sentences:  Assuming that the basis of color difference perception was the statistical error in matching the appearance of a given color stimulus he conducted an extensive experiment with one observer, the result of which was expressed in the CIE chromaticity diagram in form of statistically derived ellipses, published in 1942 (See Fig.1).However, the resulting Friele–MacAdam–Chickering color difference formula proved less effective in predicting perceived color differences than formulas derived on other bases.