FMRIB Technical Report TR00MJ1

Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB),

Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital,

Headley Way, Headington, Oxford, UK

This report describes a mathematical approximation to convert from
T to Z and F to Z statistic values. The approximation is asymptotic as it is
becomes more accurate for higher values of T, F and Z. Since these values
correspond to low values of probability, p, the actual transformation
uses log(p) as the intermediary, and so can be calculated with normal C/C++
float variables, without having problems with underflow.

- Introduction
- Z Score Approximation

- T Score Approximation

- F Score Approximation

- About this document ...

Mark Jenkinson 2004-01-21