> Can any one suggest how to draw a ROC curve? I am trying
 > to compare two digital systems used in dental radiology.

ROC curve fitting is described in the following papers:

  Dorfman DD, Alf E.  Maximum likelihood estimation of parameters of
signal detection theory and determination of confidence intervals
rating method data.  J Math Psych 1969; 6: 487.

  Dorfman DD, Berbaum KS, Metz CE, Lenth RV, Hanley JA, Dagga HA.
Proper ROC analysis: the bigamma model.  Academic Radiol 1997; 4: 138.

  Grey DR, Morgan BJT.  Some aspects of ROC curve-fitting: normal and
logistic models.  J Math Psych 1972; 9: 128.  

  Metz CE, Herman BA, Shen J-H.  Maximum-likelihood estimation of ROC
curves from continuously-distributed data.  Stat Med 1998; 17: 1033.

  Metz CE, Pan X.  "Proper" binormal ROC curves: theory and
maximum-likelihood estimation.  J Math Psych 1999; 43: 1.

  Swensson RG.  Unified measurement of observer performance in detecting
and localizing target objects on images.  Med Phys 1996; 23: 1709.

Any or all of our University of Chicago software for ROC analysis can be
downloaded without charge from
<http://www-radiology.uchicago.edu/sections/roc>.  Most of these
programs are available in Windows, Macintosh and generic
UNIX/workstation/mainframe versions.

  Charles Metz