Hi, What you observe of perfectly normal, although seldom mentioned. In "low statistics" case the chi-square method will underestimate the "area", while the log-likelihood will not (there are actually two ways of defining the chi-square method - one will underestimate the "area", the other one will overestimate it - the method used in root will always underestimate, as you could see). With "high statistics" any method gives "proper" results (but still the log-likelihood gives "more proper" results). Conclusion - always use log-likelihood if you have low statistics or a lot of "noise" in your spectrum. Best regards, Jacek.
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