15.64.31.7  ERRORS   - Set the error array DY or DZ.  If this is specified
for HBOOK and the histogram contains no errors, garbage may  be  collected
in  DY.   For  2 dimensional or RICE histograms the ERROR=SQRT(Y).  If you
omit ON or OFF then ON is assumed.
(Default:ERROR=ON when REVISION>4.30)