[silver_sun]

Their section on "Dataset limitations" says that the study "Only captures bugs with Fixes: tags (~28% of fix commits)."

Just worth noting that it is a significant extrapolation from only "28%" of fix commits to assume that the average is 2 years.

[tremon]

Why? A sample size of 28% is positively huge compared to what most statistical studies have to work with. The accuracy of an extrapolation is mostly determined by underlying sampling bias, not the amount of data. If you have any basis to suggest that capturing "only bugs with fixes tags" creates a skewed sample, that would be grounds to distrust the extrapolation, but simply claiming "it's only 28%" does not make it worth noting.