This function is used internally to compute the estimates of betas.
A matrix or numeric data.frame consisting of an n (no. of items) by N (no. of methods) matrix of measuremnts.
See Jaech, p. 184.
A vector of length N (no. of methods) containing the estimates of beta.
Richard A. Bilonick
Jaech, J. L. (1985) Statistical Analysis of Measurement Errors. New York: Wiley.