A method for analyzing a target nucleic acid includes diluting nucleic acid targets and filling pico to femto-liter sized wells such that they contain a single target nucleic acid and one or more amplification reagents, amplifying the target in the individual wells, distinguishing wells containing amplicon from the target and amplicon from a variant of the target generated by polymerase error by using two differently labeled-hybridization probes, one hybridizing to the target and one hybridizing to a specific variant of the target; and analyzing target amplicons.