The equation for the attenuation of a gamma-ray flux passing through a path of length x in a sample with linear attenuation coefficient u can be expressed as I = I0 e ^-u*x. For most environments, the value of u is not known and must be estimated by measurements.

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The extinction coefficient can refer to a few different measures how strongly a distinct medium absorbs light at a particular wavelength. The two most commonly referred to are molar absorptivity (which measures absorption per molar concentration) and the mass attenuation coefficient (which measures absorption per mass density).

ɪf the regresion coefficient is the coefficient of determination, then it's range is between 0 or 1. ɪf the regression coefficient is the correaltion coefficient (which i think it is) the it must lie between -1 or 1.

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