chi2¶
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gammapy.stats.chi2(N_S, B, S, sigma2)[source]¶ Chi-square statistic with user-specified variance.
\[\chi^2 = \frac{(N_S - B - S) ^ 2}{\sigma ^ 2}\]Parameters: - N_S : array_like
Number of observed counts
- B : array_like
Model background
- S : array_like
Model signal
- sigma2 : array_like
Variance
Returns: - stat : ndarray
Statistic per bin
References
- Sherpa stats page (http://cxc.cfa.harvard.edu/sherpa/statistics/#chisq)