Chi-square statistic with variance computed from model amplitudes.
This statistic is equivalent to CHI DVAR, except that
the variance is estimated using the background and source model
amplitudes rather than the observed counts data:
sigma(i)^2 = S(i) + [A(S)/A(B)]^2 B(i,off) ,
where B(i,off) is the background
model amplitude in bin i of the off-source
region. See CHISQUARE for more information,
including definitions of the quantities shown above.
The background should not be subtracted from the data when this
statistic is used. CHI MVAR underestimates
the variance when fitting background-subtracted data.
Specify the fitting statistic and then confirm it has been set.
sherpa> STATISTIC CHI MVAR
sherpa> SHOW STATISTIC
Statistic: Chi-Squared Model Variance
- sherpa
-
bayes,
cash,
chicvar,
chidvar,
chigehrels,
chiprimini,
chisquare,
cstat,
get_stat_expr,
statistic,
truncate,
userstat
|
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