ASSESSING BIG-BANG NUCLEOSYNTHESIS

Systematic uncertainties in the light-element abundances and their evo lution complicate a rigorous statistical assessment. However, using Ba yesian methods we show that the following statement is robust: The pre dicted and measured abundances are consistent with 95% credibility onl y if the baryon-to-photon ratio is between 2 X 10(-10) and 6.5 X 10(-1 0) and the number of light neutrino species is less than 3.9. Our anal ysis suggests that the He-4 abundance may have been systematically und erestimated.