Why are you interviewing the plumbers? If a million plumber and no programmers applied, you would immediately reject every resume and not interview anyone. No

Why are you interviewing the plumbers? If a million plumber and no programmers applied, you would immediately reject every resume and not interview anyone. Note that this assumes none of the plumbers have been working on teaching themselves software development in order to make a career change and thus do not have non-work evidence of competence.