# Prof. Hanns Ludwig Harney

## present interests

### My present interests: "Bayesian Statistics" and

"Item Response Theory"

**Hanns L. Harney, Nov. 10, 2016**

In the year 2003, my book entitled
"*Bayesian Inference - Parameter Estimation and Decisions*"
had been published by Springer Verlag at Heidelberg. A second revised edition of this book
is now available. We hope that the revisions clarify and allow for a better
understanding of the leading idea:

A symmetry relation, called form invariance,
between the observed events and the extracted parameter values. When expressed by a group
of transformations, this symmetry defines the Bayesian prior to be the invariant measure
of the group.

One chapter of the second edition of "*Bayesian Inferene*" is devoted to
Item Response Theory which formulates a model of measurement in psychology
needed for intelligence and competence tests. This chapter concerns,
e.g., the so-called PISA tests, the Program for International Student Assessment.
It assigns well-defined statistical errors to the competence parameters extracted from
the tests.

H. L. Harney pursues Item Response Theory in cooperation with Dr. H. Bernshausen (University of Siegen, Germany), Dr. Ch. Fuhrmann (University of Wuppertal, Germany), Prof. K. Harney (University of Bochum, Germany) and Prof. A. Müller (University of Geneva, Switzerland).