

PA 765: Correlation 
  Beside Pearsonian correlation (r), the most common type, there are other special types of correlation to handle the special characteristics of such types of variables as dichotomies, and there are other measures of association for nominal and ordinal variables. 
  Also, there is partial correlation, which is the correlation of one variable with another, controlling both the given variable and the dependent for a third or additional variables. 
  Eta, the coefficient of nonlinear correlation, known as the correlation ratio, is discussed in the section on analysis of variance. 
 www2.chass.ncsu.edu /garson/pa765/correl.htm (3727 words) 
