Common mistakes

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==Too many fit parameters (forgetting the overall normalization parameter)==

If the system is not overdetermined, then fits will not represent a true minimum.  With more than a few fit parameters, the system must be very overdetermined using many experiments or scattering angle ranges, etc.

A common mistake is to forget that Gosia must fit the overall normalization of cross section to measured gamma-ray counts.  (This effectively includes the total beam dose, detector efficiencies, etc.)  If, for example, Gosia is used to try to fit the B(E2) in a two-state calculation, this overall normalization parameter will adjust to allow any B(E2) value at the chi-squared minimum.  The fit will converge, and Gosia will not report an error, but the fitted B(E2) will be meaningless.

Using Gosia 2 in two-state systems with measured yields for both the projectile and the target is designed to overcome this problem.