attribute 2 the second normal distribution 110 may have a mean parameter u03bc i1 125 that is constrained to be less than 0 the mean of the response propensity distribution for masters of both attributes and a fixed variance of 1 the area above u03c4 i1 for this class may be equal to u03c0 i xr i2 in the ordinary fusion model parameterization the third normal distribution 115 may represent examinees who have mastered attribute 2 but not attribute 1 the third normal distribution 115 may have a mean parameter u03bc i2 130 that is constrained to be less than 0 the mean of the response propensity distribution for masters of both attributes and a fixed variance of 1 the area above u03c4 i1 for this class may be equal to u03c0 i xr i1 in the ordinary fusion model parameterization as in the fusion model the probability that an examinee that has not mastered either attribute will successfully execute them is equal to u03c0 i xr i1 xr i2 as such three parameters may be estimated for this item in the parameterization u03c4 i1 120 u03bc i1 125 and u03bc i2 130 each of these parameters may be directly translated into u03c0.