Biological techniques can be used to reconstruct the stemmata of text traditions. Here, we describe methods for assessing the reliability of the results. We use compatibility matrices to detect sections of the text with different patterns of transmission. By constructing stemmata from subsets of increasing size, we estimate the minimum amount of data needed to produce a reliable stemma. We use consistency indices to assess the overall reliability of the stemma and the level of support that individual variants give to the stemma. Bootstrap analyses allow us to reject features of the stemma that result from only a few variants. We apply these techniques to the stemma for the Miller's Tale in Chaucer's Canterbury Tales.