Plot of quality values (QVs) for approximately 2000 bp of mitochondrial DNA from a downy woodpecker (S. Edwards, unpublished data). The sequence was determined by the shotgun approach starting with a long PCR product (S. Edwards, J. Gasper, W. Nelson, J. Avise and D. Pollock, unpublished data). QVs are based on details of peak morphology, height and consistency across similar nucleotides both in the trace under scrutiny as well as across traces spanning homologous bases, and are equivalent to QV=−10 log(Pe), where Pe is the probability that the base is an error. Thus a QV of 30 indicates that there is a 1 in 1000 chance that the base in question is incorrect, or, alternatively that the probability of a correct call is 99.9%. Typically, NIH genome projects require a QV of 40, although some genome publications have used minimum QVs of 20. The flatness of the threshold of QV at approximately 90 is a function of the base‐calling method.