I have a system that compares two items and produces a match score. Scores below a threshold are manually inspected to determine if they match or don't(imposter). Scores above the threshold are assumed to match with no further testing. Can I use the distribution of imposter scores below threshold to estimate the imposters above threshold that were assumed to match (false accept rate)? If no, how can I estimate the false accept rate without testing those above threshold? During system test where all items were verified the distribution of imposter scores was lognormal.