A method and device are described for analyzing a sample for the presence of a nucleic acid wherein the sample is amplified, illustratively using PCR, in the presence of a fluorescent probe capable of providing a signal related to the quantity of nucleic acid present. A nucleic acid sample is amplified in the presence of the fluorescent entity, and the fluorescence intensity is measured at each of a plurality of amplification cycles. Scores are obtained from various tests performed on the fluorescence data, and the scores are used to determine whether the nucleic acid is present in the sample.