          Chi-square statistic with variance computed from data
          amplitudes.

The chi2xspecvar statistic is equivalent to chi2datavar

("ahelp chi2datavar"), except that when the number of counts in a channel bin is less than 1, the variance is set to 1.

sherpa> set_stat("chi2xspecvar")
sherpa> show_stat()
Statistic: Chi2XspecVar

Set the fitting statistic and then confirm the new value.

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

December 2013