Correction of correlation and covariance between simple concepts
Imagine that we would like to know the strength of the relationship between two opinions (the variables of interest), for example, job satisfaction (f1) and life satisfaction represented by the correlation coefficient ρ(f1, f2). This coefficient cannot be obtained directly. One can only estimate the relationship ρ(y1, y2)between the observed variables, i.e. the responses to questions with respect to job satisfaction (y1) and life satisfaction (y2). The relationship between f1 and y1 and between f2 and y2 will not be perfect because of the measurement errors (e1 and e2). The standardized effect of the variables of interest f1 on y1 is called the quality coefficient (qi). This simple idea is presented in Figure 1. A more elaborate measurement model will be presented later.