Sample size is 21 and they used Kruskal–Wallis (which is parameter free). Might not be the best tests (iirc. it's usually recommended for the exact combination of ordinal+nominal but I'd have to check) but it's suitable enough.
Also I don't think convenience sampling is bad in this case (and they clearly indicate they did it etc.) as it allows you to control for TDD experience and the like. I'd even go further and say the typical "lol students as participants" isn't an issue either.
"How effective is test-Driven Development.
Making Software: What Really Works, and Why We
Believe It" by Turhan et al. is a good meta analysis if you want more studies.
As an aside I like the fact that this is a replication study and that there have been a couple of these.
I mean worst case you can uses theses studies to guestimate better priors for your own Bayesian analysis :)
Also I don't think convenience sampling is bad in this case (and they clearly indicate they did it etc.) as it allows you to control for TDD experience and the like. I'd even go further and say the typical "lol students as participants" isn't an issue either.
"How effective is test-Driven Development. Making Software: What Really Works, and Why We Believe It" by Turhan et al. is a good meta analysis if you want more studies.
As an aside I like the fact that this is a replication study and that there have been a couple of these.
I mean worst case you can uses theses studies to guestimate better priors for your own Bayesian analysis :)