[someguydave]

As far as most state law in the US is concerned, 'formal training' for engineers is generally defined as having an accredited degree. 'informal training' for engineers is generally defined as having a documented apprenticeship under someone of known competence.

[__derek__]

Ah, that "informal" was referring to a particular body of training. I took it to mean its standard English definition, which would extend to self-study and working as a junior developer.