Any maths afficionados/penface s on here that can help me with this?

It's about a book on test equating and scaling, but something is missing between Newton-Raphson and chained linear methods.
What the blinking flip could it be?:

The authors then describe IRT true score equating, the Newton-Raphson techniques that the chained linear methods, for observed score and true score methods.

Posted By: Worzel Scrimmage, Sep 12, 19:29:10